I received a WhatsApp message with a link which directed me to make a card payment

I received a WhatsApp message with a link which directed me to make a card payment. I followed the link and the payment was successful. Rain agent is telling me they are unable to locate my pay2, it's invalid. How?? When I have proof of payment from my bank. I am sitting without internet access yet have just paid. I don't want to mention the terrible internet connection I am experiencing daily, especially at night