SIM 508 Pads

Those are the mounting tabs that hold the module to your PCB. You should have a hole in your PCB at each of the 4 locations, and then use a nut & bolt to fasten the module to the PC.

ok thank you GSM man i think that it has relation with the ground or power

They should be grounded

but on the datasheet it is not mentionned that this pad should be grounded