Carphone said it was mindful of the tougher High Street conditions
Carphone Warehouse shares have fallen 13% after the retailer's latest trading update disappointed analysts.
The firm said it had added 109,000 broadband connections in the three months to the end of March, which was below forecasts of about 128,000.
Carphone also said its full-year profit would be between £225m and £220m, slightly below analysts' expectations.
However, the number of mobile phone customers rose by 12%, which was more than expected.
"Our performance over the last three months has been good in a slower consumer environment," said chief executive Charles Dunstone.
He added that Carphone was expecting to make "considerable further progress" in the year ahead, although the firm was "mindful of a tough consumer environment".
At close its shares were down 13.32%, or 35.50 pence, at 231 pence.