Brother, I got myself into a similar situation like yours. Actually, just two weeks after submitting my document, I did not recall if I had signed the cc payment form or not so I went ahead asking them what to do, here is their response.
Liaison, Liaison
Dec 11
to me
Good Afternoon,
It will take 8 to 10 weeks for the request to clear the FBI security process before we are able to see the request in our system. You may visit our website at fbi.gov/checks. On the right, under Forms and Links, you may print off the credit card form. Please fill this out, include your full name, the original mailing address, your contact information and your signature. You may fax this to 304-625-9792 or scan and email to this address. If we receive the request and it is insufficient, it will be placed on hold until we receive the updated payment. Once we receive the payment it will start the processing date over again. If you send the payment in at this time, before your request clears security, the information can be updated and no delay will take place. Even if you sent in the payment with the original request, and send the fax, you will not be changed twice. Thank you!
#11065-Kim
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If you need further assistance please contact:
Federal Bureau of Investigation (FBI)
Criminal Justice Information Services (CJIS) Division
Biometric Services Section
Customer Service Group
(304) 625-5590
Office Hours Monday-Friday
8:00am-8:00pm EST
liaison @ leo.gov
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So... I sent them another payment form via email address and they confirmed they forwarded that to the processing department.
I applied it from Canada.