It could have been his way of trying to lessen the pain for him. He might still be having feelings for you, but you are not available since you are married, so, no pun intended, to him talking to you is to no avail. It could be that each time he hears your voice, the feelings he has been trying to suppress resurface, and he does not like feeling emotional pain. Also, and further, he could have felt resentment towards you for putting him in this position in which in his true emotional self he is not happy that you got married, but as a polite person he felt obligated to congratulate you on your marriage. I do not know - I am just saying it could have been the case. And then the "cold turkey" silent treatment was a way of expressing that resentment.