Motorola MT8733 issue slow speeds

I replaced my Xfinity modem/router with a Motorola MT8733 listed as compatible with 2.5 gig. Upon connecting and running a speed test, I'm getting only 700-800 down and yes 5 up. 5. The Xfinity router was much faster on both sides. I contacted online chat which was no help.

I did see this in this forum...how do I get in contact with someone who has a clue about this..."

the supported upstream frequency range of the Motorola MT8733 is switchable between

5-42 MHz and 5-85 MHz (sub-split and mid-split) and is not compatible with high-split (5-204 MHz). This means that Xfinity will have to provision your device either for sub-split or mid-split and not for high-split.

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Any help?