Disturbance in MCI phone bill sms transmissions

In the past, before every phone bill distribution, the company would send sms message to its subscribers informing them of the amount they owed, as well as payment id number so that they would pay the bill via an ATM terminal rather than a bank branch, but this time it seems some subscribers have received their printed bill before the sms message, although some have received none at all.
MCI has around 16.5 million postpaid sim card subscribers.
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