I am not happy with the Service I got from MTN store

I am not happy with the phone I bought on a contract, On the the 19th of September 2020,I bought a Huawei P40 lite on a 36months contract. I wanted to use the phone for work and business purposes,since it's the latest phone, now the phone doesn't have play store,it has an App called Findorra,I was never inform that Findorra App that Huawei is using now is not the same as play store and that the phone might not accept the Apps I want.,so the phone doesn't support a lot of the Apps that I need for work and business purpose .on the 20th of September 2020 I went back to MTN store Lakeside Benoni to info them about the problem I am experiencing,i advised the lady that was helping me that I don't want to cancel my contract I just want to exchange the phone for a Samsung phone because Samsung has a play store and it supports all Apps ,the lady told me that the store manager doesn't allow for an exchange to be made because I have already inserted my SIM card,and if she even tries to exchange she will get a writtern warning,the reason I was given doesn't make sense to me .the phone isn't even a day old but they refused to exchange the Huawei P40 lite for a Samsung . I am really unhappy with the service I received. @MTN please advise on which steps I should take to get the matter resolved. Because I don't want to be pay for a useless phone for 3 year.