I was getting 10+ spam calls a day a couple of months back. They all originated from overseas numbers and I was pissed off that there isn’t a way with iOS at least to block certain countries. Like no one from Malta is ever going to call me so why can’t I just block Malta.

I resorted to using Do not Disturb mode allowing my contact list to ring. It’s worked out great, I have missed a couple of blocked caller numbers that I would have liked to have taken but they always leave messages. And the spam calls have more or less dried up now.