Q: I recently sent my iPhone 5 direct to apple as thats how it was purchasedto be repaired and they sent me a replacement, I inserted an activated sim card and I noticed it said 'No SIM'?

I recently sent my iPhone 5 direct to apple as thats how it was purchasedto be repaired and they sent me a replacement, I inserted an activated sim card and I noticed it said 'No SIM', I carried on trying to activate the iPhone until the iPhone said that I couldn't go any further without a sim card and to insert one, there was already a sim card in, I thought it would have been the sim card so I ordered a new one and activated it but the same happened again so I called apple and they told me to do a few things which did t work, I couldn't even restore the phone, and it was wired because they couldnt recognise my imei number, they said they were going to call me back because the telephone line was bad but they haven't, also, I don't know if it has been updated to ios7 as I didn't have either iPhone when it came out and I haven't been able to get on to the iPhone properly since I received  I've already been 9 days without a phone I don't want to wait any longer, what can I do? Please help!