You need to be very careful with your approaching AAC. Personally, I stay off the phone, period! Everything I do is in writing and sent CMRRR. The descriptions of avoidance after verbally asking for proper validation are indicative of AAC's lack of proof or their realization that they make more money by simply moving onto a more acquisant and accomodating "debtor."
I suggest that anyone dealing with AAC, or any collection concern do the following:
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Stay off the phone no matter what. If they call, don't answer.