Sorry about the issue. If you go to the domain that you want to upgrade in your dashboard, in the lower right, you see this:
Click ‘Change’ and you can select the plan you want to upgrade to and add payment info there.
Thank you very much Domjh
At least I found out how to pay
Even tried to mamake the payement
Yeyt in the end I did not get it whether the payment has gone through
Anyway thank you very much once again
MK