Is the transaction that enables a customer to borrow three pounds from Vodafone in exchange for deducting two and a half pounds, and then three pounds are deducted from him upon recharging, considered usury?

If the company lends to the client and collects the loan with an increase, this is usury (riba) and is impermissible, unless the increase is in exchange for effort or work expended by the company. However, if the company provides communication services at a higher price for deferred payment, there is no harm in this, as it is selling the utility of communication at a deferred price that is higher than its cash price.