Looks like they offer a SIP trunking feature at the bottom. Their pricing looks pretty expensive as well.I guess not so much yay?
What is it that yay offers you that 3CX doesnt that you require?
All you need is a SIP Trunk - looks like yay is it's own phone system.
Founded in 2005, when VoIP was an emerging technology, 3CX has gone on to establish itself as a global leader in business communications.