By initiating a call-back, you are making the request conform to the rules covering remittances requested entirely by telephone, which permits oral pre-payment disclosures. You follow up with a written receipt, as also required.
Based solely on what you have said and without reviewing any actual disclosures, I think the practice is fine.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8