MTN denies selling off numbers

After getting between 10-15 calls a day from various marketing companies trying to sell insurance, funeral policies, etc, I asked these people where did they get my number. The standard reply: "from MTN ma'm. So I tried their call centre - they could not assist and disconnected me every time. So I reached out to them on Twitter, and aha!!! Instant response: Please check your dm's: So I did and communicated via messages with NM. It was immediately denied, telling me that MTN do not sell databases or disclose my number to anyone. So I wanted to know why all these telemarketers would lie, as they specifically stated that they obtain my number directly from the MTN list?? MTN's answer: That's not true. So I supp**** a few numbers which bombarded me with calls each and every day, turns out that one of them belongs to the MTN Sales office. NOWHERE did I give permission for them to contact me. So this MTN person requested my mobile number in order to stop any calls from their sales side. I specifiically requested the document where I gave consent, but they kept ignoring me, sending me a thumbs up with NOTED!! I have responded with the same request, it is unacceptable that they just remove my number from their list, but what about all the rest? Or do they indeed have contact with the people from the insurance, funeral policies, etc and will also remove it from their lists? Do they have a right to invade one's privacy on a daily basis just because they're my service provider?