Yes, I remember receiving 2 line emails that sent me into Hyperventilation Land. My peace was disturbed and I was a wreck.
Eventually, my solution became this:
1) Serenity Prayer, said more than a few times (and then once more, with feeling
)
2) Take a deep breath
3) Play the tape all the way through...ask myself "What does this mean for me in the long run?"...generally, my answer was: not a thing.
4) Post on SR to get some much needed perspective
5) See if I needed to modify certain things in how I'd set up my boundaries (or my email blocks).
I think you can apply a similar strategy when you receive little blips out of nowhere that try to ruin your serenity. Is it possible to have that number blocked? Or perhaps, as you suggested, is it possible to change numbers?
Take a breath, take action and soon enough you'll be back your serenity.