Telkom unhappy client

I took a laptop on contract it arrived,it is super slow and I haven’t even loaded the programs I will be using on it for school and work. Told them at Telkom what I needed the laptop for. I went to give it back Sun,13/11/22 after I called and told them the problem. I was told I cannot change and take it back and get another package with a functioning laptop. Please help as I really don’t want to pay for 36months for something I am not happening about.