is it illegal for t mobile to record conversation in store without permission?

If the recording was of a telephone convresation, only one party needs to consent to the recording, and the other party does not need to be informed of the recording, so there is no recourse if that is the case.  As to whether or not there is any remedy for recording a conversation between 2 people, not on a phone, I don't know of any specific law that prohibits it, and I would think that the same kind of laws apply as apply to the phone call.  Often, businesses record calls and conversations for quality assurance and/or for training purposes.  As to whether you have any legal recourse, the question to be answered is "what are your damages?"  Even given that you may be offended that you were recorded, how are you damaged or injured?  Put yourself in the role of a juror and ask yourself what kind of remedy/award would you give to some stranger who presented these facts to you?  In short, I would not take your case if you came in to see me about it.