Problems exporting a JT number to the new Co-op mobile network should be over by mid-March.
The competition and regulatory authorities in Guernsey and Jersey have worked together with JT to tackle the problem.
But, they say it is disappointing that they have had to intervene.
Bosses of the Channel Islands Co-op and Sure complained to the watchdogs that JT customers wanting to move to the new mobile provider were unable to bring their existing number with them.
Mobile Number Portability is crucial to encouraging competition because it means an individual can change provider but still keep their number.
The regulatory authorities say JT originally gave them a May 2026 deadline to resolve the problem, but that has now been brought forward to 17 March.
Tim Ringsdore, who heads up the JCRA, says it was essential to resolve the problem as soon as possible:
"The earlier implementation date will provide JT customers with an additional choice of mobile provider sooner than previously expected.”
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