Eckoh, which already manages the distribution of calls into Ideal's UK and overseas centres, is expanding its service to include web, phone, email, social media and web chat channels.
The group first signed a contract with Ideal to provide its hosted interactive voice response system in 2005 and extended it in 2014 to cover its new Ideal Shopping business in the US.
It has already begun work on the latest deal and will roll it out in stages during 2016. Private equity group Blackstone bought Ideal last September.
Eckoh has announced several new deals since November last year, including the extension of its business with an unidentified leading global financial services company last month.
The company is aiming to expand the range of call centre-related services it offers to include latest-generation technologies as well as incorporating its flagship secure payments service.
Eckoh’s patented CallGuard technology, which allows users to key in their own card details whilst connected to a centre agent, prevents human access to personal information.
It is part of a growing drive to offer customers a comprehensive, "one-stop shop" service.
Eckoh's chief executive Nik Philpot said: "We have been providing services to Ideal Shopping for over a decade and during that time both companies have evolved in size, market reach and offer.
"Ideal Shopping recognised Eckoh's ability to provide a full omni-channel service for its customers in the UK and US, and has entrusted us with this important part of its contact centre transformation."
The company is not changing its profit forecasts as a result of the deal but said it would further underpin its financial performance for the year ending 31 March 2016 and beyond.
Shares in Eckoh rose 0.75p, or 1.7%, to 45.25p in early London trading.