Hi @moti n ,
please take a look here: Delete an Azure billing payment method
Depending on the type of Azure Subscription. There are some types you can't remove the (last) payment method. In this case you can modify/change the payment method (Replace the credit card for a subscription to a previously saved credit card).
Please take a look here how to check which type of Azure Subscription you are running : Check the type of your account
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten