Problems with receiving calls

[MustangLady]

Got Sony Ericson mobile and for last couple days cannot receive calls on it. All diversions are off and from what I can see all settings suggest able to make/receive calls, have credit on it but if anyone calls it gives recorded message saying This phone is Switched Off !!! Any suggestions before I tredge off down to a phone shop see if they can resolve it. Thanks

[factor-fiction]

Do you have a blue tooth receiver in your car?
Or maybe there is no signal at the times people ring