The cyber-attack on TalkTalk could cost it up to £35m in one-off costs, the company has said.
Following the hack, which divulged some users' financial details, all customers of the telecoms group will be offered a free upgrade.
Chief executive Dido Harding said that despite the hack, TalkTalk was "well positioned to deliver strong and sustainable long-term growth".
The firm expects full-year results to be in line with market expectations.
TalkTalk shares had jumped more than 13% by the close of trade on Thursday, but were still down more than 20% compared with their pre-hack value.
Speaking to the BBC, Ms Harding said: "The estimated one-off costs are between £30m and £35m - that's covering the response to the incident, the incremental calls into our call centres, obviously the additional IT and technology costs, and then the fact that over the last three weeks until yesterday our online sales sites have been down, so there will be lost revenue as a result."