Blackberry problem, someone help?

So I have a Blackberry Pearl Flip 8230f, and all of a sudden it stopped recieving signal, even though I always have signal with it, it stopped, also everyone else with my same carrier ( Appalachian Wireless ) still has signal, I have rebooted it and done a handheld wipe, nothing works also I made sure that my connects were on. However twice since it has messed up it's showed no bars but a 'D' underneath where the bars of signal should go, someone help, please? :(

Is it a GSM or CDMA device? If it's GSM, have you tried a different SIM card?

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