Manager can't do his job properly

I purchased a phone at mtn a Huawei p10 lite because they had a good deal going manager of the store assisted me in getting everything sorted, they advised me it's dual sim an stuff that was one of the main reasons for purchasing it, later to realize no dual sim app is activated on the phone an after calling into the store they advise that Noone of the phone's that mtn stock is dual sim an I should take it to Huawei in canal walk to have it fixed an I should pay for it, why should I if the fault lays by them if they advised me in the first place I would not of bought it