Vodashop cant accept back their contract phone that they gave a bad recommendation on

I was very specific to Wilson, one of the sales consultants guys that i need a 2 years contract phone specifically for the camera sinse i need to use it for my youtube videos and he came with LG k61 so i signed the contract and i went home only to realise that it doest serve its purpose. The videos are very dark and blurry. I tried to take it back to the store for a better one, and the manager was very furious and said i cant take a phone back simply because of a dissatisfaction even if its still within 7 days. I tried to explain to him that its not dissatisfaction issue its a bad recommendation by Wilson and i believe they were just trying to get rid of it since no one wanted to buy it.

The manager said they wont take it back because i have already signed the contract. Please help, this is a two years contract on a device that i cant even use.

Thank you Oliver