Sent in early 2018, the texts encouraged EE customers to use the ‘My EE’ app to manage their account and also to upgrade their phone.

The company stated during the investigation that it had sent the texts to provide service information so they were not covered by electronic marketing law. However, the ICO ruled that the messages contained direct marketing.

Andy White, director of investigations at the ICO, said: "These were marketing messages which promoted the company’s products and services. The direct marketing guidance is clear: if a message that contains customer service information also includes promotional material to buy extra products for services, it is no longer a service message and electronic marketing rules apply."

White added: "EE Limited were aware of the law and should have known that they needed customers’ consent to send them in line with the direct marketing rules."

An EE spokesperson said: "We accept the ICO’s findings, and we’re working to improve our internal processes. We’re committed to ensuring our customers are fully aware of their options throughout the life of their contract, and we apologise to the customers who received these messages."

Under electronic marketing regulations, companies can only send marketing messages to existing customers if they have given their consent and are able to opt out of marketing messages when their details are first collected and in every message sent.