UMTS stands for Universal Mobile Telecommunications System and is the successor of GPRS. UMTS is also called 3g. UMTS promises speeds similar to ADSL and so many new possibilities arise. Think of image telephony, watching movies, wireless internet and e-mail everywhere, but also faster sending of photos, presentations and files. Theoretically, UMTS speeds can be reached up to 2 megabits per second.
GPRS means General Packet Radio Service
The abbreviation GPRS stands for General Packet Radio Service and is a technique for exchanging data between the provider and the GSM phone. It is the forerunner of UMTS. The payment is made over the dates that are received/sent, not for the time one is online.