Bad SIM cards

About 2 weeks ago, I purchased a MTN sim card from PEP Home in Southgate Mall. I have not given my new number to anyone, not even my own mother. Yes, I keep getting spam calls from the same person, different extensions, every other day. This is ridiculous. I have another Mtn sim card and when I got that one from the Mtn store directly, non of this happened.

These are the numbers: *** *** *** *** *** ***

Where I check these numbers on my true caller, they are ****mers.