The use of Dynamic DNS is completely irrelevant. If you changed nothing else, then the
problem lies 100% on the new internet provider.
Did you install a new router, or is the old one still being used? If you changed the router,
then it may require some configuration (e.g. SIP ALG off, ports forwarded, etc.).
Is there a difference in the type of broadband technology being used (e.g. DSL, 3G, etc.)?
3G/4G requires some optimization, I can give you a list.
What port is being used for SIP in your RRC's? If 5060, try changing it to something else.
Make sure that RTP is turned on to continuous on both RRC's.
The problem is for sure on the provider or router. You need to locate that problem, but
the couple optimizations I mentioned may help a bit.
73,
Mitch DJ0QN / K7DX