I've been with Primus for calls for years and never had a problem with them.
I'll be moving the line rental to them come the end of the month, because BT have decided to charge me over 100% more for line rental starting this month. TalkTalk and Sky are also increasing their line rental beyond inflation.
A licence to print money, particularly for someone who just uses their landline for broadband Internet. Mobile internet can't compete with its caps.