can't verify phone number, everytime notify me that it has been in use

[Huan0]

this is what I got

"This phone number is already in use. Please click cancel and try a different number."

I don't know where I used this phone number, can't remove that account?

[Ying-Jung0]

same here. Please advise!

[Alpha3]

Samehere, called customer service more than 5 times and waited more than 1 month. The only answer I get is "HANG ON TIGHT".