Horrible customer service

Good Day

I bought a home router at Telkom Mompati Mall Vryburg, on the 2nd of April 2025 however I can't use it, and I went back to the shop the following day because I can't use the router. The manager is not useful and refuses to help me, saying the box was already opened and he was the one who opened the box in the shop, now he can't take it back and I should go and sell it at Cash Crusader so that I can get my money back.