A text message scam is catching people off guard by posing as one of their friends with an alarmingly simple trick designed to dupe the receiver into paying for mobile phone top-ups

The deceitful SMS chain has several variations, but they all seem to start with a message that claims to be from "Sarah".

The fraudulent texts are intended to pray on and manipulate mobile users that have a friend or family member with the same name which, considering its popularity, represents a huge proportion of the UK.

The messages also frequently claim that the sender has been in an accident of varying severity. Most describe a scenario that led to 'Sarah' suffering broken bones and other injuries.

Some of the texts forego using the Sarah alias however, instead posing as the victim's mother, as in the following example found by ActionFraud:

"Mum i did try and phone from some else phone signal is really bad, there has been a terrible car accident. I'm in the ICU ward in hospital my phone ain't switching on and needs charging. I'm on this mobile number please make sure you reply to this number, my friend didn't make it he died before we got to hospital and his sister's fighting for her life. Mum i had my seatbelt on, i've got a head injury but i'm ok. Going into Xray to be seen, please make sure you message me back and don't phone cause mobile phones aren't allowed here so please text in case I'm in there. I will go outside and phone you mum its really bad i need you to do me favour before it's too late, as soon as you get my text please reply by text i need you to do me a favour mum, time is running out and i need you to do something mum."

Those caught out by the scam have noted that 'Sarah' later asked them to buy a top-up voucher code and send it back to her. The scammers are then thought to be cashing-in these codes on their own mobile accounts - this can go as high as £20 at a time in some cases.

In a blog post last year, ActionFraud noted that under no circumstances would a "family member be forced to use a mobile phone that required credit to activate it."

It also offered simple advice for victims: "If you receive one of these text messages, don't send any codes or money, delete it and report it to us."