Most expats don't use landlines here at first because they don't have a permanent house for quite some time.
It's better to get with the local operators that run with mobile communications = mobile phone lines.
DST, you can get a number right away and it doesn't cost much. Or with another company that is PCSB.
Only about ~BND30.00Â Â BND5.00 (in your credit to start), you can register a new prepaid line and use it within 2 hours.
While with postpaid line (Monthly payment) will be of different process, so you will have to talk with your service provider's customer service.
Both have a lot branches around Brunei, and most usage & charges are quite straightforward.
However if you would like to setup a landline, you will have to call TelBru, which you can also check their website or branches location. You will have to make a minimum payment of roughly $13 monthly, while additional to pay for plan for e-speed (internet connection).