setting up a ppp session using a usb vodacom 3g modem

Im trying to setup a ppp session with a usb 3g E220 modem (vodacom) to routerOs 3.22 which is running an a pc.
all that happens is its says status initializing modem
Ive phoned vodacom and I have the modem init string and the dail nr for my modem, but I cant get it to connect, is there somebody that can help me or that has done it before.