The FCC Enforcement Bureau has fined US telco Sprint $7.5m (£4.5m) for failing to honour customers requests to opt out of phone and text marketing communications.

Since 2003, Americans have been able to opt out of receiving most telemarketing calls by putting their phone numbers on the National Do-Not-Call Registry. A spokesperson for Sprint told CNET the issue was caused by “technical and inadvertent human errors”.

This is the largest settlement of its type ever seen from the FCC. Additionally, Sprint has to develop and implement a two-year compliance plan, including changes to operating procedures and policies, appointing a compliance officer, and training staff on the matter.

“We expect companies to respect the privacy of consumers who have opted out of marketing calls,” said Travis LeBlanc, acting chief of the FCC Enforcement Bureau. “When a consumer tells a company to stop calling or texting with promotional pitches, that request must be honored. Today’s settlement leaves no question that protecting consumer privacy is a top enforcement priority.”

This isnt the first time Sprint has come under scrutiny on issues of consent. In 2011, the telco was fined $400,000 following an investigation into consumer complaints about receiving marketing calls after they had asked to be placed on Sprint’s internal Do-Not-Call list.