Online gone wrong

I brought phone online on mtn they where suppose to deliver 2 deal Samsung but they not available the advice on how about i take the Huawei nova 70plus they where the same price now my instalment is now double from what i agreed on also i didn't get my contract hence the put my cellphone number as my email address i regret taking the phone online maybe if i went to the branch would be better their customer service is bad they will give you the run around transfer you from one line to another saying it's not their department i need my contract as well as explanations why im suppose to pay more than what i agreed on.