Routing Across canopy usuing VoIP

I have 2 cisco 2811 routers. At the head end I have F0/0 (created F0/0.355 encapsulation dot1q 355 which matches Remote end.

The remote end handles interface vlans for voice and data with dhcp helper addresses.

I have QOS on the F0/0 on each end (was not allowed to put QOS on sub-interfaces)

I tested my VoIP and found that my phone calls cut out but it was intermittent

Does anyone have any suggestions to address the intermittent phone cut outs?

Sorry, are you having problems with VoIP with the 2811s wired together, or is there a Canopy network between them?

I am having trouble with VoIP accross the canopy
Do I need to run PPPOE on my sub-interfaces?