I have a 5s - and a friend of mine who also has a 5s has been unable to receive my calls or texts for the last week. I can receive calls and texts from him but he isn't receiving anything from me. Both of us are Verizon customers. Once I realized this I then texted and called him from my son's cell phone - and he received both. Any ideas?
There can be many reasons for this occurring. Let's start with some of the simplier possible causes on the devices. Have your friend with the iPhone 5s delete you as a contact and then try calling again. If this does not resolve the problem try deleting him as a contact and retest.