The phone operators were given six weeks to draw up the Codes of Practice in April, following concerns by UK telecoms regulator Ofcom over mis-selling in the sector.
Ofcom was particularly concerned about slamming - where consumers are switched from one supplier to another without their knowledge and consent, usually after a cold-call from the new supplier.
The regulator will investigate allegations of mis-selling on a case-by-case basis, and if companies breach their obligations it may require them to give written undertakings as to their sales and marketing practices.
Ofcom also has the power to impose fines of up to 10% of turnover in the event of continued breaches.
The regulator will review the obligation after two years.