No help from Summer Mobile and MTN

I took out a contract Summer Mobile (MTN) , I had ordered a Huawei nova 10se dual sim and they delivered a single sim phone... I called the customer service the following day which was on Tuesday the 12th of February and the phone was delivered Monday the 14th, they told me to take it instore... Went to MTN Potchefstroom in Mooiriver Junction they said they can't assist me cause they're a franchise I'll have to go to MTN Klerksdorp I'm from there now and it's the 17th of February they Also didn't wanna help me cause I had done the deal online.... I don't know what to do anymore cause I don't want to pay for a device that I don't want... Can I please get assistance in all this problem