Call Quality Issue

HI,

We experience:
-degraded incoming voice quality and potential outgoing voice quality
-dropped calls in the middle of conversation
To save you the trouble, I'm pretty good in voice communications (MOS, etc), VoIP, network, and computer stuff in general.
Our setup is business COX with 25 down / 5 up. We have a CISCO 2821 router with CISCO 3750 switches trunked. Our quality of service is enabled and our pings to 8.8.8.8 are stable. We've wired one phone line into the base station and even this line has degraded issues. This points me to the Ooma cloud or between our site and ooma cloud.
Any recommendations? do you folks have service level agreement tests between the base station and the ooma cloud? Should we change codecs? server locations?

Any help will be apprecited.

I didn't find the right solution from the Internet.

References:
https://www.ooma.com/forums/viewtopic.php?f=16&t=21180
Motion graphics animation agency

Thank you.