As I understand it 3g accounts use dial-up to connect to the system,
/meaning they have to dial in/.

The package that is required to do this is PPP. Install it with the
Synaptics package manager, then set up your account information as you
would in doze. I have not used a dial up connection in years but I have
to set-up dial-up to use my 3g modem device, not that hard.