SORRY.....Am replying to my own message.
Trying to make payments to other sellers, I have come to realize that this is endemic to all sellers, not just a particular one.
I made a mistake earlier......the payment site is BillDesk, and not Billpay. The problem is this....the field for the name as on credit card is too short as it can only accept 15 characters including spaces ! The field for the 3 digit security code is also 15 long, which is absurd for a 3 digit code.
This appears to be a Ebay's problem and not BillDesk, as the coding for this page is incorrect. Unless Ebay makes changes to this page, I for one will never ever be able to purchase from here again.
If somebody from Ebay management reads this, please ask coder to make the name field longer ( 20 characters at least ), while the 3 digit code field can be shortened to accept 5 characters max. My own full name including spaces is 16 characters long, and will never fit into the current 15 character max field.
Ebay, I have been here a long time, but if I cannot purchase from now on, it is time to say good-bye.