Adultery

it depnds upon the contents of the chat.

changing phone number will not help you if case is sustainable.

Whatever that you have done so far, there is no law to punish you. The burden of proof is on the husband to prove that you had s*xual intercourse. You are saying that the lady is pestering you even after her husband has come to know of everything. Probably both are hand in glove to blackmail you. The best thing is that you keep away from both of them hereafter. You delete from your own mobile whatever evidence is there.