I gave blood about a year ago in a drive sponsored by the Red Cross. They call me at least once a week. Got a new phone but kept same number and have blocked their various Atlanta phone numbers.
The American Red Cross calls my number from MANY of their different numbers several times a day several times a week! If I put that # in my contacts so I will know who is calling with that number, that number is ALWAYS different the next time so I can NEVER block it or ignore the call!