Shares in TalkTalk plummeted by 17% in early trading after it reported a £75m loss and warned that full year profits will be at the lower end of its guidance.
Nevertheless, TalkTalk guided that full-year earnings would be at the lower end of its £270m to £300m range.
The company added 46,000 net customers in the first half after a 29,000 fall in the year-ago period, on the back of stronger demand for its fixed low-price plans (FLLPs).
Headline EBITDA for the 1st-half was GBP 95 million (excluding MVNO loss), compared to GBP 144 million a year earlier, with a statutory operating loss of GBP 42 million, compared to a year-earlier profit of GBP 44 million.
A futher £59m exceptional charge was incurred for costs associated with implementing changes to the group's organisational structure.
Chief exec Tristia Harrison said: "When we simplified and reset the business in May we said our priorities were growth, cash and [earnings before interest, taxes, depreciation and amortization] in that order". "Our revised strategy of focusing the business on fewer, clearer priorities is re-establishing TalkTalk as the value provider of choice in the United Kingdom fixed connectivity market". The mobile customer base fell by 61,000 in the first-half as TalkTalk prepared to launch a new proposition.
TalkTalk said its broadband base grew for the third successive quarter and customer churn, the rate at which people leave for rivals, had improved year on year from 1.5% to 1.3%.
Harrison said the firm had achieved this despite "an uncertain economic environment".
There was also a £31m charge at its mobile business as a result of a strategy review.