Can't receive calls from some numbers

[Anonymous]

I can receive calls, but not from some numbers. My closest friend usually cannot ring me, though he can text me. Random numbers can also not ring me - inconvenient when it's a delivery driver with a notification or query. I've tried going in to an O2 shop with my friend: we were told it must be the his network. We then go into an EE shop, where we are told the problem must be with O2. Understandable that networks want to pass the buck, but not at all helpful. I just want to reliably receive calls. Is it O2? Is it my phone (an iPhone 4S)? Many thanks for any insights.

[gmarkj]

So some other things to try:
- Put your sim in another phone (if you have one) for a few days and see if the calls come through
- Get a new sim (call customer services or go into a shop) which rules out if the sim is faulty

[Lets-sort-it]

Thank you again, I don't have another phone but I will try the O2 Shop later this week. I did try and call customer service but they are too busy, saying that wait is more than 15 minutes and then the lines just hangs up. I guess they don't want people to wait. But thank you. Your advise is much appreciated. 

[Rusty99]

I just moved from o2 to Smarty on the Three network last week and was able to make calls to all networks including o2 but friends who are on o2 could not make a call to me they got a message "calls to this number are not being connected". After much fafing about with Smarty and trying to get o2 to look into it I got a call from an o2 engineer who had fixed the problem. He said that my phone number originated with Vodafone ( that was the very first provider I used when I got my sim) and that when o2 ported my number over to Smarty they added a couple of extra digits on my routing number. They do this for o2 numbers apparently in order for them to work, but should not of done with my number. Now I can receive calls from o2 sims. It took a lot of persistance with Smarty to get them to investigate this properly, but it paid off in the end. I almost gave up and changed back to o2.

[Wun88]

This has been happening to me for a couple of years & i just found out why on the new iphone update. Go to phone>silence unknown callers! It says calls not saved in contacts will go to voicemail & silenced if you turn it on however it was doin it to people i did have saved but this has resolved it