Q: Can i receive phone call on iphone 5s while using internet?

Hello

I was using internet via WiFi with my iPhone 5s, however I could not get the incoming call. I was contacted to another number, and was told that my number in iphone is not reachable. During the time they tried to reach me, I was on the internet via Wifi. Once I got off from the net, all was working fine, that`s I could receive phone calls.

Is ti possible that while using internet via Wifi or data, I cannot receive or to make calls on iPhone 5s?

regards

Endre