How do I cancel my Apple Music subscription from my old phone if it is broken and unable to use?

If you did not add an extra trusted phone number to your Apple ID, you must use account recovery.

See >>> https://support.apple.com/en-ca/HT204921

You could also try moving the SIM in your broken phone to another device and send an SMS to it.

See >>> https://support.apple.com/en-us/HT204974

Log into a different device on the same Apple ID, click here, and follow the instructions.

(181144)