i have tried changing my payment method but i am still getting There is a billing problem with a previous purchase

If there is a billing problem with your previous purchase, you might be unable to make purchases, download free apps, or use subscriptions. To fix the issue, change your payment method. If you can't change your payment method, you can redeem a gift card and use the balance to pay for any unpaid orders.

If you have followed all the steps and instructions in Related Article: If a message says 'billing problem with previous purchase' or 'verification required' and if you still need help, get more help and assistant from Apple directly, see Contact Apple for support and service -> Contact Apple for support and service – Apple Support (UK)