How can I activate my old SIM card?

I had to ship my Apple iPhone 5S back to Apple so that they can send me a replacement. I had purchased the device at full price only for 4 months ago, and it already had several manufacturer defects (both hardware & software related). I have my iPhone 4 and 4S, however the iPhone 5S SIM card is not compatible with the iPhone 4 or 4S. I have my SIM card for the iPhone 4, is there a way I can temporarily reactivate this SIM card until Apple sends me a new 5S, so that I can have a working wireless device? The AT&T website only has an option for upgrading my phone or activating a SIM card for a "new" order. If no options, then I need to suspend my service. Again, the options on the AT&T website for service suspension apply only to lost or stolen devices. Anyone have any suggestions?