A few people I work with have been happy with ViaTalk (not sure if VT supports BYOD.) Just started Axvoice, went ahead & signed up for a year, seemed a bit cheaper.
Axvoice features and VM could use some polishing/ enhancing.. Otherwise, service seems good. Support is via email chat, they may call you if necessary but they do not provide numbers to call, (maybe because they are in India?)
From site on codec:
Axvoice supports G711u & G.729 codec. By default your account is enabled for G.711u. To have G.729 configured please contact
support@axvoice.comAfter the year is up I may try CallCentric or
VoIP.ms.