The personal jurisdiction analysis can be very fact-intensive, and you need to consult with an attorney about the specific facts of your case. For example, do you regularly sell products or services in PA? If you have continuous and systematic contacts with PA, then there would be general personal jurisdiction. If not, then have you sold or offered to sell any products or services in connection with the accused trademark? If so, then there may be specific personal jurisdiction. If not, then you may be able to contest personal jurisdiction (but the plaintiff could file a lawsuit against you in CA where you reside). Also, please note that you could waive personal jurisdiction if you have already answered the complaint instead of filing a 12(b)(2) motion to dismiss for lack of personal jurisdiction. Again, assuming that no answer to the complaint has been filed yet, you need to consult with an attorney about the specific facts of your case as soon as possible so that he or she will have enough time to work out a legal strategy before the answer is due.
As for your comment that you "have already changed the name," I assume that means you have stopped using the accused mark. While that means there will be no future damages, the plaintiff could still maintain a lawsuit for prior damages as well as for an injunction in case you decide to start using the accused mark again.
If you have stopped using the accused mark, it may make it easier to settle the dispute. Again, you need to consult with a litigator with trademark experience immediately.
This answer is for informational purposes only. It is not intended as specific legal advice regarding your question. The answer could be different if all of the facts were known. This answer does not establish an attorney-client relationship.
As my colleague notes, the imposition of personal jurisdiction is fact-dependent inquiry, and you haven't provided any facts to work with about what the allegations are.
Courts can find general jurisdiction when the defendant's activities in the forum are "continuous and systematic," or specific jurisdiction where there are "minimum contacts" with the forum state. Jurisdiction can also be based on the defendant targeting the forum state's residents.
I assume your company has a website and your domain name allegedly infringed on the plaintiff's TM since you state you "already changed the name." You can't negate the past harm by changing your website name, although you can at least stop the damages from accruing.
You're going to need to hire your own TM litigator, and very quickly to avoid a default. Realize that even if you do succeed in getting the case dismissed from the PA court, the plaintiff can refile in a CA court.
PLEASE READ THIS BEFORE YOU COMMENT, EMAIL ME OR PHONE ME. I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls, and you shouldn't expect me to respond to your further questions if you haven't hired me. We need an actual agreement confirmed in writing before any attorney-client relationship is formed. This answer doesn't constitute legal advice, and shouldn't be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.
Most states have what is called a "long-arm jurisdiction" statute, that essentially provides a way for the courts of one state to exercise jurisdiction over non-residents of that state. Whether the jurisdiction is being properly exercised in your particular case is a fact-based inquiry that depends on what factors have to be present under Pennsylvania law for Pennsylvania's long-arm statute to be exercised under Pennsylvania law. You will need the assistance of counsel to determine if jurisdiction has been properly exercised in your case.
To answer your second question about the effect of changing your name, the answer is that changing your name MAY not resolve the lawsuit altogether. It depends on what the plaintiff is really after and the facts of your case. If you are no longer using the allegedly infringing name or mark, you have effectively cut off the claim going forward. However, the argument could still be raised that you're liable for the period of alleged infringement. Often it is more important to the trademark owner that the alleged infringement cease. Collecting damages is often a secondary concern for the trademark owner. Technically if changing the name means that you are now using a different d/b/a ("doing business as" or assumed name) then the plaintiff would not need to re-file the lawsuit, but rather it could move to amend its complaint to reflect that name change.
You should consult an attorney ASAP. Also, you indicated that you are being sued in Pennsylvania. Many trademark lawsuits are brought under the federal court system, even though the lawsuit is physically venued in a particular state. If you are being sued under the federal court system, as opposed to state court, you do not necessarily need to find a PA attorney but you should try to find someone who has experience in handling trademark cases before federal courts. Also, it is unclear when you were served with a complaint, but please note that the law requires you to either answer the complaint or to make a motion such as the motion you asked about to dismiss on jurisdictional grounds soon after the complaint is received. So don't delay.
The statements made herein are not intended to be, nor should they be relied upon, as legal advice regarding your specific case or matter. No attorney client relationship is implied or should be inferred from this communication. Please consult with an attorney who can advise you appropriately regarding your case or matter.