36 months at all costs even at the expense of the client

I had to get a new cellphone contract, the model of phone I wanted was out of stock(Oppo A74).The sales agent and her colleague both recommended another phone promising that its the newer model and is better than the phone I actually wanted and is an upgrade(A77) ,as I left the store I realized while using the phone that its worse in every possible way.I immediately went back to the store as this is an error on the sales team and not mine, I was told by the lady once I sign there is nothing I can do, I wanted to return the device as they said it is an upgrade of the phone I had previously, it is clearly not worse camera, worse chipset, worse gpu and a 720p display as opposed to a full HD screen, I returned again two days later to the store explaining the situation to the sales lady who said she was acting manager and was told there is nothing to be done, I will be taking this further as I won't be locked into a 36 months contract with a phone that was sold to me with false information and treated so poorly when all I ask is for them to take this back and supply a phone with better specs than the A74 like I asked in the first place.