concept on logo is : high visibility, easy to recognize and unique font setting that emphasize the product. You can of course decorate it with all kinds of symbols like swooshes, globes, planes and what have you, but I believe in keeping it simple.
Imagine a 3x2 foot poster of a modern business person calling looking happy and this logo in the bottom right corner. Maybe a slogan like: "Stay connected with Prepaid SIMS"