1. It is not clear as to when you have cleared all the debts of your son at Dubai, why and how the said Banks at Dubai are harassing you and if you have cleared the entire outstanding amount why the banks have not issued No-Due certificate to your son.
2. However, you can collect the statements of accounts of all the Banks where your son had credit card outstanding to ascertain how all those Banks are still claiming payment when you have already cleared their dues.
3. If there are genuine outstanding lying in the credit card accounts of your son at Dubai, they can initiate recovery proceedings in India by filing a recovery suit.
4. If your son further visits Dubai, they may prosecute him as per law of Dubai for not clearing his outstanding dues which he shall have to contest fittingly.