HELP on a MPx220's GPRS

[Guest lowi82]

I live in Guatemala. I have a subsbscription with one of the largest cellular companies here. I recently bought a MPx220 and am having trouble with it detecting the GPRS on the network (No G shows up). I am most certain its the networks problem, although I do have access to the GPRS on my older phone v300. And another curious fact is that when I insert a SIM card from the other phone company down here, it detects GPRS with no problems. Is there anyway around this by tweaking something on my cell phone?

THANKS,

LOWI.