THE icons used to visualise moods in texts, be it a happy of frowny face, could leave users with massive bills.
Called Emoticons, the little images are used to bring a bit of colour and humour to someone's message.
But recent complaints filed on consumer website MoneySavingExpert have revealed a large number of people have run into issues while using them.
It appears to be a problem that affects certain models of phones, making it a manufacturer, rather than a network, issue.
Older handsets made by Samsung are known to be at risk, with the issue surrounding how the phone interprets the emoticons.
The icons can be converted into multi-media service messages (MMS), which can leave the user being charged up to 40p each depending on the network.
MoneySavingExpert say users have revealed they have been charged for using 'emojis' despite having all-inclusive text allowances in their plans.
A post regarding the issues on the consumer website explains: "Samsung says that every device launched since April 2014 has a default setting that classifies emojis as an SMS and not an MMS. However, it says that for older devices, such as the Galaxy S4, emojis will lead to messages being converted from an SMS into an MMS.
"It adds that a warning message is displayed to inform the user that their message will be sent as an MMS.
"According to Ofcom's latest Incidence of unexpectedly high bills report, conducted between July 2013 and May 2014, of the 5,696 people questioned, 4% said they experienced higher than usual bills because they had sent picture messages not included in their monthly text allowance."