Declined return

On the 25th of July I purchased a power bank that has 65watts I don’t know much about watts and technological things I was advised after the charging the power bank that I was supposed to buy a 100.0 watts power bank as my laptop has those watts.I bought a power station that has 300 watts on Saturday after I had returned the power bank.Provided them with proof of the purchase for the power station and advised that I did not use the power bank to charge any devices however I was told that they declining my return and I’m not accepting that They should have checked if I did definitely use the power bank to charge any devices.I want my money back as I did not use nor damage the power bank that I had purchased I’m really not a happy customer as I usually make purchases from take alot