Rude MTN representatives

My mobile phone contract is ending, and I receive frequent calls from MTN about an upgrade.

MTN is represented by a firm named www.rewardsco.com. The 'Rewardsco' representatives are unpleasant when you decline their upgrade proposal and abruptly hang up the call. I truly believe MTN should choose their partners that respect South African citizens and avoid being rude when no deal is taking place.