Hi MIKAmacey3597,
Since Music stops streaming but phone calls work on cellar data, let's make sure you have cellular data enabled for Music.
You can check on your Apple Watch under Settings > Cellular > Music.
If this is disabled, enable it and try streaming Music again.
You can find other information that may be helpful, here: Set up cellular on Apple Watch - Apple Support
If you have followed the steps correctly and you still have the issue, let us know if you get any specific alerts or error messages when trying, as those may help us determine what might be causing the issue.
We also recommend restarting your device and keeping it updated as those steps assure you have cleared out any minor software issues and are running the most current version.
Restart your Apple Watch - Apple Support
Update your Apple Watch - Apple Support
If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support
Cheers!