Xbox game pass purchasing question

been thinking for a while about subscribing to xbox game pass,I have stopped subscribing to xbox live gold for over a year now and thinking about coming back getting xbox game pass ultimate as it includes xbox live gold too.But I don't like to enter my
credit details onto my console or my paypal details either.I usually by credit online with cards usually £50 cards and redeem them so the credit I purchase the is on my xbox live account ready for me purchasing games etc.Can I purchase using the credit I have
on my account to buy game pass subscribtion every month,just would like to take advantage of the £1 for 1st month joining offer but it asks for adding a credit/debit card or paypal details..currently don't have any credit on my xbox atm but don't want to purchase
a £40/£50 card online to redeem if I'm unable to get the xbox game pass this way,can you only purchase this offer by entering my personal card/paypal details..

:)