Poor customer service

I bought a service kit online; I gave all the details about the car I was buying service for, Service kit came with wrong air filter and plugs. I emailed the store regarding the wrong sizes, I stated on the email about what exactly is wrong, was told to bring it in for exchange. Now they refuse to exchange the wrong air filter and plugs, Saying the do not change individual but the whole kit, Oil and petrol filter is used already now, I'm told told to buy air filter and plugs since they cannot help me with exchange.