"No Service" issue on iPhone5s on iOS 8.0.

I recently updated my iPhone 5s to iOS 8.0. I've been on iOS 8.0 for about 3 days and this morning my phone said "No Service". I have switched it on and off, did a hard reset, took the SIM out, switched to airplane mode, reset the network settings, reset all settings, swopped SIMcards, nothing works. I am not at my laptop today to do a complete wipe and re-installation of iOS, and if I do that, will I not just get the same bug again and again? I googled and it seems to be a common problem with iPhone6 and the newer iOS 8.0.1 and a way to fix the problem will be to downgrade to iOS 8.0...the problem is that I am on iOS 8.0. not 8.0.1 so downgrading to iOS 8 (which seems to be the common fix for the issue) won't help as I never updated ot iOS 8.0.1 and is still on iOS8.0. Can I downgrade to the previous 7.whatever iOS? Does Apple still support that version? Or what else can I do? Any other bug I can live with, but the "No Service" issue is hampering my business, my work flow, clients can not reach me...Ho can I fix this ASAP please?