Howdy folks, So I was having the same registration problems others were with callcentric. I had downloaded pretty much every voip/sip software and was trying them all out. At first 3cx worked fine but then it stopped working at all and I tried many times to get it to register to callcentric. Including reinstalling etc. After reading here that it can work fine I dumped all the voip apps and loaded 3cx again and it started working, but only after a few more tries. This is on a motorola backflip. Now that it's working, I have horrible echos. The one thing that I found that fixed it was to use the aLaw G.711 codec. However, it seems without the uLaw G.711 codec enabled, I can't receive incoming calls. Any ideas?