Apple Music - changing device for studnt accont

That is not how it works.

You can use the Apple Music subscription on all your devices that use the Apple ID that has the subscription.

Devices with a different Apple ID cannot use that subscription.

Users are encouraged to use a single Apple ID for all their devices, so that services can make use of that link.

You can probably sign out of the Apple ID on that phone and sign in again with the wanted Apple ID, but you also lose access to products and services that were tied to that other Apple ID. As a bit of a caution: You are not supposed to switch accounts constantly on a device, and certainly not when using services like Apple Music, as doing so may lock you out for that device.

You can use one Apple ID on up to 10 associated devices, including using the Apple Music subscription (but one device at a time), if you want.

To make a clean start, it may be best to Restore your device to factory settings - Apple Support, so that you can start over with entering the correct Apple ID credentials.