2000/250 Mbps plan stuck at ~80 Mbps upload — no OFDMA channel provisioned on XB8

I'm on the 2000 Mbps download / 250 Mbps upload plan using the rented Xfinity XB8 gateway (Technicolor CGM4981COM). Download speeds are fine (matching or close to 2000 Mbps), but upload is consistently capped around 80 Mbps — nowhere near the 250 Mbps I'm paying for.

What I've found after checking the gateway's own connection status page:

- Upstream: only 4 bonded channels, all using legacy ATDMA/QAM modulation at low frequencies (16–35 MHz). All 4 are locked with clean power levels, but there is NO OFDMA upstream channel present at all.
- Downstream: locked correctly, including the DOCSIS 3.1 OFDM channels (722 MHz and 957 MHz), which is presumably why download speed is fine.
- Xfinity's own Broadband Facts label for my service address (checked directly at xfinity.com/broadband-labels) shows a typical upload speed of 293 Mbps for this exact plan — well above what I'm getting, and confirming this speed should be achievable at my address.

This looks like a mid-split/Next Gen upload provisioning issue — my account or gateway doesn't appear to have been switched over to the OFDMA upstream service profile, even though the XB8 fully supports it and my address's disclosed typical speed confirms the infrastructure should support it too.

What I've already tried, all without resolution:
- Visited an Xfinity retail store in person
- Called Xfinity phone support
- Xfinity chat support
- Had an on-site service technician visit

Every one of these gave me the same generic WiFi/signal troubleshooting steps (router resets, reseating cables, etc.). None of them checked or mentioned OFDMA provisioning or the upstream service profile on my account, which based on my own diagnostics looks like the actual root cause.

I'd like this escalated to Advanced Repair or Network Provisioning/Engineering specifically to check:
1. Whether my account is provisioned for the mid-split/Next Gen upload tier
2. Whether the correct bootfile/service flow has been pushed to my gateway's MAC address to activate the OFDMA upstream channel

Happy to provide my full name, service address, and gateway MAC address via direct message. Thanks for taking a look.