World is not enough acheivement problem

[Johnno124]

I got all the cell phones from QoS but the achievement didn't pop. I went back through every level and it says that I have got them all except for Casino Royale level. It says that I have 3 of 4 cells in the level. I went through the level completely 3 times and couldn't find it. I also looked at some walkthroughs online and they all said that there are only 3 cells in the level. I also started a new game but there are no phones in any of the levels. I think that they might be linked to your gamercard. Any help would be greatly appreciated.

[McGoogles]

I think you need to trigger a checkpoint once you find a cellphone in order for it to count (except for your last one). Try clearing your cache and keep looking for that last cell phone in Casino Royale. It should be there. If you still can't find it, delete all of your save files off your hard drive and start a new game.