Did I send a reminder message to the math department and then return it to T?

It should be fake. At the end of the payment message received by the borrower, there is the word unsubscribe back to T, which is probably a false message sent by some commercial platforms in batches, because the beginning number segment at the end of this kind of message is generally 106X, which belongs to the spare number segment of the three major operators and is specially used for sending short messages in batches.