What do I do when I get a message saying "phone number already exists" which doesn't allow me to reach out to a sitter?

I've been trying for weeks to reach out to a sitter. I may have accidentally created 2 accounts -- that's the only reason I can think of that I get this error message that "phone number already exists for another account" but I don't know what to do about it. If I have another account, I don't know how to find it. I just want to reach out to a sitter but the system won't let me! Very frustrating app and no support.