this might help:
CPE - customer premises equipment
PLDT Fiber -> CPE -> ethernet
Bayantel Fiber -> CPE -> ethernet
ethernet cabling -> network balancer -> core network switch/es -> access switches -> workstation
by the way, how is the voice service delivered to your domain?
Using a separate link?
If same na link for data and voice, I'm not sure if this topology would work kay dili man ko familiar sa capabilites sa balancer.
But if your links are IP VPN/MPLS links and your CPE is a router, you need to advertise a public address on both links. Easiest solution is to have one of the links as a redundant/fail-over link.
And if data traffic is the only traffic sa 2 links then the topology with the balancer using both at the same time should work.