Wife brakes my trust

Good Afternoon sir, last 12 days i am very much tortured. actually i read a Whats up chat of my wife. She chat with someone his old school friend but the conversation is shown more than a friend. i further inquire to my wife and she told no relationship among them. after investigation i got a call detail of my wife's number and found that they talk to each other almost 1-2 hour on a day or 5 days. based on the call detail. i call to the guy and told him that i have had all data that he has a illegal relationship with my wife. then he not admit on the relationship. then i ask to my wife and based on the conference on that boy she also agreed, and told me that it was just friendship type of relationship and they exchange kissed over there.I would also like to tell you that entire episode of reveling the fact from that my wife admitted is based on the assumed data.But that boy not admitted i am trying to meet but also not ready to meet . he also assured me that he is no more interfere in our family relationship. my wife is also admit that they have gone in the deep sexual conversation in chat and even exchange of picture ( which might be nude or semi nude) but they never meet; I have given my best and quality time to her and always try to chill but she have done big cheat to me. I was trust her a lot but somehow it’s all broken by her. my inner instinct are not allow to live with her more as she destroy my faith and trust too. The mobile number she is using now is taken under my name so can I take whatsup chat and video detail after taking court order (without suite any case) how could I take written undertaking from my wife that such thing are not repeat in future.in legal care and if I suit a divorce case, can I kept my both child with me. please suggest :- i) what i can do against my wife who is cheated to me. we have two kids 6/8 yrs old son and daughter too. ii) what legal action i can take and how! iii) how could i get the chat detail from service provider