someone is using my company name to advertise their dog outfit . I did a goggle search for my company name i get their ad

You state that "Doggone Couture" is your trademark, but you don't state that it's registered. Apparently you'vebeen using that TM as a TM on ads and on your website, and not just as a domain name, so you probably at least have common law rights to that mark. You may have trademark and unfair competition claims you could assert, depending on what your company's rights are and what the eBay user's use is, but without specific details, it's hard to advise you. Another company's mention of your company can be nominative fair use. For example, is your company used for comparative purposes, like "our dog clothes are better than Doggone Couture's dog clothes"?

Even if you don't want to have a lawyer contact them and you want to do it yourself, you should contact a lawyer so you can get some specific advice regarding what your rights are and what if anything you should do about this eBay use.

Disclaimer: Please note that this answer does not constitute legal advice, and should not 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. This answer does not create an attorney-client relationship.

What do you mean you "own" the name? Do you have a trademark, either state or federal?

Without seeing the ad or your website there is no way for anyone here to give you any useful advice. You should consult with an intellectual property attorney for further guidance.

There's nothing more to add to Ms. Koslyn's super response other than this: if you send a cease and desist letter -- even a very nice one -- that letter provides the recipient with the right to file suit against YOU in what's called a "declaratory relief action" which, essentially, puts the question before a judge as to who has the legal right to use the trademark in question. You assert that you do, the other side asserts that it does and so the judge (or a jury) get to decide the matter. It is not just a good idea to for you to hire an intellectual property litigator to reach out to the other side, it's pretty much required. Good luck.