Upgrade to 1000 Mbps plan but slow upload speed at 6 Mbps

Hi,

We just upgraded our Xfinity internet plan from 75Mbps to 1000Mbps last Thursday. After reactivating our modem, we see a boost on our download speed, but the upload speed is still similar to before, and it seems to be capped at 6Mbps. From the website, the 1000Mbps plan is supposed to have 35Mbps upload speed. And, the modem we are using can support up to 151Mbps upload speed. I was wondering if Xfinity is still in the process of upgrading my internet? Or, this is an issue with the equipment and the cable connection?

Thanks,