Hi Csaba
Welcome to the eForum. You've come to the right place for help.
There are a finite number of possible causes for your troubles, so if we rule out as many as possible, we'll have a better idea of what we need to fix. The potential causes are:
Modem Fault
Sim Fault
Signal Strength
Network Fault
Computer Fault
You've already ruled out a modem fault as you experience the same problem with the Sim in a 3G phone. Did you use the phone as a tethered modem, or just have problems surfing on the phone itself? If it wasn't as a tethered modem, and you still had the problem then this would rule out a problem with your computer. If it was as a tethered modem, we'd still need to determine if your Mac was causing the problem, by trying the modem in a different computer.
In regards to signal, I've checked the coverage in your area and it does look to be good, apart from a small patch close to you, but mainly centred around the nearby church. It's possible that you're in a black spot, could you take your Mac and modem to a different area and see if you have the same problem. If you don't have the problem elsewhere, this would indicate that the signal is the problem as I've checked the sites in your area and they are currently running at a 98.3% success rate for data. If you do have problems elsewhere, we'd need to replace your Sim. If you go into a Vodafone shop you'll be able to get a free replacement as yours would be faulty.
I'm really glad I could help and I'm sure you'll be up and running in no time.
Cheers
J
eForum Team