Using Spotify connect with streaming over cellular data instead of wifi data.

You aren't streaming over cellular, it is not possible. Sonos, even when using the Spotify app, streams directly from the source via your local broadband internet connection.

My phone has an unlimited plan, but my home internet does not. Would prefer the data to be used from the phone.

In otherwords, when i shutdown my wifi, I can stream Spotify to my phone using cellular data. However to connect to my Sonos, I am connecting through wifi and my concern is i'm using wifi data and not the phone data.

As stated, Sonos can only stream via your local network.

Also, the Xfinity limit is massive (1 TB). You could stream 32 streams of 320 kbps audio 24/7 for an entire month and only use 3% of a Terabyte.

I know, for this month so far, Iam at 1.2 terebytes and climbing. We have been using Netflix more (new cable boxes) and started using Sonos around Christmas time. I'm trying to figure out what my be gobbling up all of that data.

Netflix, even over the Xfinity box app, counts against the cap. I'd look there first. Sonos, even maxed out at 32 separate streams to 32 separate speakers running 24/7, would only be a small fraction of 1 TB.

Will do. I thought that as well, but wanted to see about spotify and sonos. Your insight has helped. Thank you.

You aren't streaming over cellular, it is not possible. Sonos, even when using the Spotify app, streams directly from the source via your local broadband internet connection.

This is correct. When you are on cellular and seeing Sonos in your Spotify app it's because the connection was made over wifi first (playing anything other than Spotify on your player will end this connection). Even if you're seeing Sonos this way and play music, the data for the music is retrieved by your players themselves, not your phone. The phone will be grabbing the metadata for the tracks over cellular, but that's fairly minor figures in comparison to music playback.

wow.. i'm glad i'm not the only one. i have xfinity as well with 1TB of data and when i got Sonos playbar with sub during christmas.. i've been using pandora on it. and on 1/28, i got warning i'm close to 1TB and then by 31st i've exceeded it. we don't youtube or netflix.. rest of time just online browsing. checking my router even with all devices offline... i'm seeing data increasing by the second... there's gotta be a way to disable all background data collection sonos is collecting from owners.

how to totally disable that besides power off?

Tbere has to be something else going on here. If you played a 320kbps stream day and night continuously for a month it would use nowhere near a TB. Maybe 120GB? And Sonos cannot possibly be collecting data of tgat order. And i think only connects anonymous data if you agree in the controller.
But no way is Sonos using anywhere near a TB in a month.