The retailer will update the City on Tuesday on how many customers it has signed up to the combined TalkTalk landline telephone and "free" broadband offer that it announced in April.
Carphone Warehouse has said the offer will be available to all customers served by 1,000 local BT phone exchanges in urban areas.
It had promised in April that customers could sign up immediately to the service, which would be available to "nearly 70 per cent of the UK population". The retailer added that the first customers would be connected by the start of July.
But new customers applying for the offer are now being told that they won't be connected until August at the earliest.
Chatrooms have been inundated with people venting their frustration over their attempts to sign up to the service, while Charles Dunstone, chief executive of Carphone Warehouse, admitted in his online blog that callers faced delays in getting through to the company's call centres.
He also confirmed in the blog that new customers applying for the service would not be online until the end of the summer.
The TalkTalk website is now advising customers interested in signing up for the service: "There is huge demand for this amazing offer and there are lots of local difficulties to deal with."
Customers who take up the TalkTalk offer will receive unlimited landline telephone calls and broadband access for £20 per month and a £29.99 connection fee.
A spokeswoman for Carphone Warehouse denied that the rollout of the offer was taking longer than planned.