CellNetwork MTN Partner - Very bad customer support! Unacceptable!

I upgraded my mobile contract in Klerksdorp La Piazza SQ at the local MTN store. 3April 2018 Tuesday morning when i went to the store i asked the sales lady for a sample or dummy phone of the Cat S60 mobile phone. She informed me that they dont have any and i can only see the phone after the upgrade was done! I took the phone and when i tested the phone i realised that the Cat S60 is a 2 year old model with no Android support as the phone will not go past Android 6.1. The phone is too big for me and I dont like the phone and the next day when i asked for an exchange the lady informed me that MTN will not take it back. What happend to the 7 day return policy and cool-off period? Cell-C and Vodacom will do the return and swop as long it is in the 7 day period. MTN refuse to help me. I am sick and tired of there very bad customer support and service. Please help and advise!