I started using InPhonex, a VoIP provider for individual customers, about 2 years ago because I needed a professional phone number in Lima, Perú, and there were very little providers for this kind of number at the time. During the first 6 months, I had disconnect problems almost every week. While discussing with InPhonex support, it appeared they changed their codec, then something was supposedly wrong with my internet line (I had another IP line from Belgium working just fine on the same phone, same internet connexion). Finally, I gave up and accepted it would be up 4 days per week, and then unreliable the 3 other days, in average.
This being said, I had a lot of business cards printed with this number, so I was reluctant on letting it go. So finally, two years later, as I managed to use another phone number on all printed stuff and got to make almost everyong forget about it... my number 705 97 28 is no more. That's US$13.95 less wasted per month. Really... not very happy.