Today my boss said that he spent quite a lot of money talking to me over the phone (~ $200), but he noticed it after a few months. I used a SIM card from another region, and the calls were ~10 times more expensive than usual.
I immediately offered to compensate for the expenses, but he expectedly refused, saying that it's not a big deal.
I didn't want to argue with him but I wouldn't want to leave it like this either. What can I do to change his decision or mitigate the situation in some other way?