I was transferred to Xbox department to cancel a subscription on a live call back and was...

Hi,Sonja! I'm Luis, a fellow Xbox Gamer . Thanks for reaching us out here.

You would need to contact support again

https://support.xbox.com/contact-us

Are you having any issues while trying to cancel it by yourself?

Head on over to https://account.microsoft.com/services

Sign into your Microsoft account and choose the Services and Subscription tab on the web page

Find the subscription you would like to cancel.

Click Manage.

Choose either Cancel Immediately or Stop automatic renewal.

Contact Support by way of chat and tell them to transfer you to the Xbox Music Pass Department to have your subscription cancelled.

I do not mean to try and overrule DrMmmPie's answer, but I would try
calling support and speaking to someone at the billing department before trying anything like cancelling a payment that has not even taken place.

you call and get billing and cancelations (each menu is different for each region)

even if you get the wrong department

they can transfer you but it does incur hold time

This link will give you step by step directions to cancel auto payment. If this method doesn't work, you will have to call Xbox support.

support.xbox.com/.../cancel-xbox-live-gold-subscription