iPhone randomly blocked contacts

A few months ago, my dad was set to pick me up at the airport

He was not responding to my calls or texts

Luckily, I was able to catch him driving by the arrivals area and flagged him down

A few days later, my  mom called and told me my dad was trying to text me and I was not responding

I tried troubleshooting and then thought to ask him to check and see if my phone number was blocked on his iPhone -- and, yes, it was (weird)

Over the past few months I have been trying to text some friends and never received responses - I figured they “ghosted” me or were just too busy

Fast forward to an hour ago when I received an email through my business’s website from one of my friends saying he hasn’t heard from me and was wondering if I was ok

So, thinking back to the situation with my dad, I checked to see if somehow my iPhone had randomly blocked how number -- and, yes, it had been

I then proceeded to go through every one of my contacts and about 25% of them had been blocked

I never blocked any of these contacts

How is this possible?