A phone network has charged thousands of customers weeks early because of a "processing error."
Mobile giant Three say a number of customers have had their Direct Debit payment collected earlier than planned.
Because of the blunder, people were charged on April 3 instead of either 15/16 April or 26/29 April, based on their standard bill cycle period.
Money Saving Expert report as many as 100,000 people are affected.
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Three said: "We apologise wholeheartedly for the inconvenience caused and if you feel that you've been negatively impacted by this, please get in touch with our contact centre on 333. Alternatively, if you contact your bank directly this can be refunded immediately."
Customers have been venting their frustration on Twitter.
Stuart Rodger said: "Tried that but you are unsurprisingly experiencing a 'high number of calls'. How about opening a crisis line for those of us severely affected?"
Magalie Cooper said: "You are always sorry but keep making silly mistakes."
One Twitter account @TheTwoJohnnys said the mistake had left them "penniless."
"This has now left me overdrawn and penny less (sic) Thanks a bunch Three. I spoke to one of your advisors regarding this and they just told me to ring my bank you'll only help me if I have bank charges cause of this!!"
John, tweeting under @Joda82, said: "What if we didn't pay the bill one month, surely we would be cut off and in breach of our contract?!
"But you guys take payments early forcing some of us to be financially troubled and what happens??! Not much!!! Surely you guys at @ThreeUK are breaching T&C yourselves."
Three set up a page advising customers what to do.
They say: "If you're worried about the lack of funds this might leave you to pay the Direct Debit, give us a call on 333 and we'll do what we can to help. Alternatively, you can contact your bank directly, and they will be able to process a refund immediately. Just as a reminder, you’ll need to contact us to manually pay your bill on or before 15/16 April.
"If you've incurred any bank charges that are a result of this Direct Debit issue, you'll need to provide us with proof and we'll arrange to refund you for any of these charges.
"The next billing cycle will be as normal, and payment will be taken on your usual payment date in May."
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