Laptop Purchase

This is my situation. I bought a laptop roughly a month ago and recently discovered it is too slow to do what i need it to do. Its an i3 and is too slow to perform the functions i need it for. i need at least i5...the first staff that assisted understood my situation and they said that i can still bring the laptop back but now that i brought it back other staff didnt know about it so they declined me because i bought it 3 apr. Please can you still help me get my money back please cause its on my credit card aswell. I need an i5 8gen atleast they said. Please help me.