Random group facebook calls with no trace

Ever so often I’ll get a group Facebook call with like one or two of my contacts in it, and then random numbers, the notification pops up for a second then goes away. Every time I went to see what the numbers were, there was no trace. No recent calls no nothing. It wasn’t too frequent so I didn’t think much of it (it usually only happens like every few months of repeated calling for a span of a few hours) but I came round to deleting Facebook (didn’t use it anyways). Just this morning at 1pm I got more spam calls, same thing although I remembered I can disable FaceTime, but this time it wasn’t any contacts, just some random email and loads of numbers. Then the notifications gone. Just like that, once again no trace.

so I disabled FaceTime, panicked I had accidentally answered and that they could see me and yeah, anyone know what’s up?