The previous poster is correct -- you are obligated and cannot just stop paying without facing a civil suit. Before you act rashly and stop paying, you should contact the attorney to whom you guaranteed the fees. While they will not be obligated to let you out of your contractual obligation, you may find that there are circumstances that would lead them to do so (such as if no bills are currently owed and none are expected to be incurred in the near future, and they may be in a position to change the financial arrangement with the client for whom you guaranteed the fees).
If you signed as a guarantor, you have a contractual relationship with the attorney obligating you to pay in the event that the client cannot. If the client is not paying and you refuse to pay, depending upon the wording of the guaranty document, the attorney may be able to collect against you without any effort to first force the other person to pay. If you still refuse payment, you may find yourself being sent to collections or as a defendant in a civil suit.
For informational purposes only and not to be relied upon as legal advice or for the formation of an attorney-client relationship.
You should also discuss this issue with the attorney who will be representing you.
This comment is general in nature and is not intended as legal advice. It does not create an attorney client relationship and obviously is not confidential. You should contact an attorney in your area who can review with you all of the relevant facts and give you specific legal advice.