Thanks for the replies, smart people! Food for thought as always....
I did contact T-Mobile but they claim they can't prevent numbers from calling me. I just hate getting those robocalls and other spamsters even though I'm on the National Do-Not-Call Registry (landline and cellular -- yes, you need to specify both separately).
I'll look into the Android thing...my Samsung runs (fitfully) on Android something-or-other....
Thanks again everyone! I feel hopeful now.