Dear Felix
We have just received your payment of $[AMOUNT, ex. 5,200.24] for [PRODUCT (S) / SERVICE (S), ex. your order of five Magna flux compressors]. Thank you for your payment. Our records, however, indicate that the total billing for that invoice (#[INVOICE NUMBER]) is $[AMOUNT, ex. 5,400.24]. Please check your records to ensure that I have not made a mistake.
Unless I hear from you, there is no need to send us a check for the remainder; we will debit your account by $[AMOUNT, ex, 200.00], to be added to your next invoice.
Please call me at XXX-XX-XX if I can be of any assistance.
Regards
Lydia