A couple of days ago I mislaid my Blackberry. Unfortunately I'd also left it with call divert enabled which meant I couldn't ring it and run around the house / car / garden listening out for the ringtone. So, having turned the aforementioned places upside down, I came to the conclusion I must have completely lost it. I called Orange and reported it lost, which led them to block the SIM card and blacklist the IMEI number. Long story short, I found the phone a few hours later and called Orange to lift the blocks.
Fast forward a few days later and I tried to make a call, but got "No service currently available". Strange, as I had full reception, so I put it down to a temporary network error and used another phone. Next day, the same thing - regardless of what number I tried to call, I got the same error. What's really strange is that I could happily browse the web via the phone, I just couldn't make calls or send/receive SMS messages.
The SIM card was fine, I tested it another phone and successfully made outgoing calls. I then tried properly wiping (factory reset) the Blackberry but still no luck. Eventually, after agreeing with Orange that it was my ageing handset that was at fault, I resigned myself to having to buy a new phone.
But then, through a bit of searching, I came across this thread. Now you can ignore the fact that it's on an O2 forum because, as mentioned, this is not a network issue. Anyway, the bottom line (and solution) is that when Orange originally lifted the SIM bar on my phone, they failed to remove the IMEI from the national handset blacklist - which explained why it worked fine in my spare handset, but not on the Blackberry.
When you call customer services (regardless of your network) ask them to double check that your IMEI number is not blacklisted on this national list of blocked handsets, otherwise you'll end up getting the "No service currently available" message like I did!
Hope that helps - if it did, then post a comment.