My number was ported from GV to Anveo in March. Localphone had an issue calling my number with a specific outbound caller ID. Some calls took about 40 seconds before the phone would start ringing. Localphone tech support reproduced the problem and took the problematic carrier out of the route.
When I tried Future9 calling my number, some calls took over 25 seconds to connect, and some calls would not connect at all. Future9 said it's Anveo's problem with porting, but I have no problem with calls from landline, cellphone, and my new GV number.
If your number works fine with other sources, then those people who cannot reach you should contact their providers (Comast in this case).