Service is definitely important, and I'm here to help! There are a few things you can try to get back up and running GrmaP.
1) Dial *228 and choose option 1.
2) Power your phone off/on.
3) Ensure data roaming/voice roaming is enabled. Steps: http://goo.gl/1HY9T
Let us know if I can help you further and keep us posted with your results.
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