******* sharing of MTN number with SPAM callers

******* sharing of number with spam callers. I purchased an MTN SIM a few months ago as a back-up (2nd SIM) in my dual SIM phone. I have never used the SIM or give the number to anyone. But I get 3-4 spam calls a week on this number. Only MTN could have provided this number.

In contrast, the other SIM that I use from a different cell company, receives virtually no spam calls at all even though this number is disclosed on the signature of every email I send and in many other places.