Vodafone is to shut down its pager business after the competition watchdog refused to approve its sale to Capita.
The telecoms giant said it was "disappointed" with the Competition and Markets Authority's decision, will no longer pursue a sale, and will close the unit down.
No jobs will be affected, but the paging division's 1,000 customers will have to find another provider.
A Vodafone spokesman said: "We are disappointed with the decision by the CMA to continue its investigation into the transfer of Vodafone's paging customers to Capita's PageOne business.
"This seems to be a surprising decision considering that this market has been contracting for some time and no other country in Europe has more than one wide-area paging network.
"Due to the expense involved with a prolonged investigation, Vodafone will not pursue the transaction and has made the decision to close down this business, which is based on ageing, standalone technology no longer supported by network vendors."
The CMA refused to rubber stamp the deal amid fears that customers would face price hikes in the wake of the deal.
The watchdog said its initial investigation, launched after the acquisition was first announced in February, found that the deal would result in a "substantial lessening of competition" given that the two companies are the only suppliers of wide-ranging paging services across the UK.
"After the merger, customers could face price rises and reduced quality of coverage", the CMA said.