I would definatley ask her about their contact. Calmy... I know that will be hard, but you won't get anywhere by yelling.
If she denies it, you need to confront her and ask what the calls are for.. Some people may disagree with me, but I like things out in the open, no secrets, there is no sense in brushing it under the rug, you need to know, therefore you will know where you stand and if you are both going to go forward openly and honest to try and fix your M.
Good luck.
me: 37 H: 44 Married for 18 years this june S7 S3 porn issues, and much more... since 7/06
Happiness can be found, even in the darkest of times, if one only remembers to turn on the light.