We chose Yay to replace a VOIP service which we had been using for several years, but which was more expensive, and a good deal less flexible, with far fewer features (eg Yay's browser based setup and management, which is good). I joined Yay and, with the number they provided, tested the link with our VOIP server and got good support while setting up their routing scheme. Porting our business number over from the existing provider ended up taking a lot of effort on Yay's part: the number was originally BT's, had been assigned to a different location, and then ported to VOIP. But Yay were persisitent with BT and gave good feedback through the process. The port came through while I was away, but having set up the original Yay number on my server, calls to the office number came through seamlessly - the only thing I had to fix was the line number appearing on outgoing calls. Only 4 stars at this stage because we have only just started using Yay as our main telephone line today - but all looks great so far.