The agency won the work in a three-way pitch handled by the AAR. It has been briefed to create email campaigns, online newsletters and microsites for the business-to-business service.
Its first task will be to support a revamp of Orange's business tariff, which was announced in February. The Orange Landline option will allow businesses to replace both landline rental and call services with a single Orange package.
The appointment of independent agency Underwired does not affect Orange's recent global agency review, which saw Havas win the advertising account for its business-to-business network.
Orange's online marketing was previously split between its direct agency Craik Jones Watson Mitchell Voelkel and AKQA, which manages its UK website.
According to a spokeswoman for Orange, the review was called because it was felt that an agency with more experience in digital marketing was needed. Both Craik Jones and AKQA will remain on Orange's roster.
Underwired will work alongside communications strategy agency Naked and Orange's in-house telecoms marketing team.