For the past two months I have been unable to send or receive calls and messages, or connect to the internet without WiFi (less very infrequent periods where very strong reception allows me to achieve full functionality).
I purchased a like new iPhone 6 recently, and immediately experienced the above issues despite the phone indicating 4/5 bars of reception and 3G. I have sent the phone away twice and had all components related to reception and connectivity replaced, but to no avail. Because I could not resolve these issues, the company replaced the phone with another, and I'm still experiencing exactly the same problems (no calls or messages unless over WiFi).
I have also been into a Vodafone store and swapped out the SIM card for a new one.
My working assumption now, is that if the phone[s] hardware was/is fine (given the repairs and subsequent replacement), and the SIM card is also new, it must be an issue with my settings/software?
One of the first questions I was asked when I initially encountered the problem, was whether my reception was strong enough. As previously mentioned, I have around 4 bars of signal strength at home, but it disappears as soon as I try to make a call. From the same locations, with my work iPhone 6 I had no issues whatsoever - nor does my partner's iPhone, which is also on the Vodafone network (ie. I can hold both iPhones side by side, on the same Vodafone plan, and one works perfectly, and mine is useless).
I've also tried reseting the carrier settings, setting up the iPhone as new, and using multiple SIM cards, but can't for the life of me figure out why the basic functions on my phone won't work.
If anyone can help me it'd be greatly appreciated.
I purchased the phone from GoodTech in Auckland. I'm getting the feeling you are correct, as the replacement phone they sent me had exactly the same problem. I have today bought another phone, this time from Noel Leeming, and the problem has resolved itself.