Why are they calling??

This is now the third time i received a call from their call centre. Yet, when i call to find out what it is about, they cannot put me through to someone that can assist. When they check the cellphone number and ID number, there is no account and if there is no account, they cannot give me an e-mail address to sort this matter out. They are super annoying because there is just no way that you can get hold of a person to take your number off their system. And if i could give them NO star, i would.