Vodafone denies hiding instructions for attacks by Egypt's ousted Muslim Brotherhood in a recent ad campaign in the country.
The operator says there is no hidden message in the campaign, which was produced to promote a special offer designed to encourage subscribers to reactivate old SIM cards.
Vodafone says the claims of covert instructions - made by an Egyptian rapper - are fantasy, and it is considering legal action.
Egyptian authorities are now probing the production firm that made the advert for Vodafone Egypt.