[Closed] Argos and their exempt from returns policy

I bought an Iphone today sim free from Argos
I later found out sim free is not the same as unlocked, it doesn't state this in their catalogue. It actually locks to the network of first sim card insertion, This is no use to me really as I use more than one network
When I tried to return it they have refused saying I was told this when I bought it. Unfortunately I want told anything of the sort though sales lady did mention

Their protection insurance for £7.99 , month

Would I like to buy a screen protector?

Would I like to take out one of their buy now pay later schemes?

Would I like to apply for their 0% credit card

That was it upon my return they said it's clearly written on the receipt it's exempt from 30 day return...it doesn't, so they changed story to say it's in their smallprint

I bought it on a credit card what are my next steps?