Hi,
T-Mobile is not renowned for being the most flexible or cheapest... However, their '
Domino Web' package is sort of copying a similar package of Vodafone. It is for people who need to have a stick ready for emergency, and use it a few times, but cannot/don1t want to commit themselves to paying a monthly fee for something they do not use that heavily. I have the similar package from Vodafone in a backup modem, should my CATV and ADSL connections fail at home, the router automatically uses the 3G. I do not pay a penny apart from topping it up once every year. If I use it, it certainly costs more than it would, but it is still cheaper than paying for X Gbyte each month if I only use it once a year... Another similar card I put in my stick, once every week or so, when I am out with my netbook, I check my e-mail on the road. Only once have I used up more than the free allowance of 50MB/month...
Certainly, if you know you are to use your 3G heavily, you can buy a normal voice SIM and activate a data package. I believe such packages are available with all three providers.
T-Mobile offers the following bolt-ons for voice packages:
Mobile broadband
Vodafone has the following bolt-ons:
Vodafone - Mobil Internet - dij_vitamax
Telenor's offers are around here:
Mobile Online 5 GB - Telenor
Mobile Online 10 GB - Telenor
Telenor has the Djuice brand aimed at young people, their Reload Net package might also be interesting:
djuice
Mobile internet is not cheap, and there are no real "unlimited" offers. But if you only use the net moderately (ie. surfing, some emails) a few gigabytes must be enough. For applications like FTP, videos etc, you can be better off by finding a neighbour who can share his internet access with you
Another point to consider is coverage, a lot depends on which carrier has best signal and bandwidth in your area. It is perhaps worth checking before purchase.