Can I sue?

You can sue him in small claims court. The court prefers a written agreement, but it is not always necessary.
I would also cancel the card to stop BOTH of you from misusing it.
On my profile there are several legal guides. I recommend reviewing the following which may be helpful to you:


Hiring a lawyer; Is it Legal? Is it Illegal?...Understanding the different court systems;
Introduction to Legal terms used in litigation; Limitations on a Lawyer’s License: What a Lawyer Can and Cannot Do……………………………..…………………………..

New York City: A Guide to the Courts……………………………………..

Commercial litigation: How to Handle a Dispute


LEGAL DISCLAIMER…………………………………………………………………..
Mr. Sarno is licensed to practice law in NJ and NY. His response here is not legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter in question. Many times the questioner may leave out details which would make the reply unsuitable. Mr. Sarno strongly advises the questioner to confer with an attorney in their own state to acquire more information about this issue.

You can sue him in small claims as was mentioned earlier. However, you may want to have an attorney (better if there is family member or friend who is one) draft a demand letter making clear that you will sue for breach of contract, conversion, and fraud, if he does not make good. That may save you the time and grief of having to go to small claims court.

I hope this helps.

Disclaimer: This answer is for informational purposes only and does not constitute general or specific legal advice, nor create an attorney client relationship.