Business use of telephones
Always best to have dedicated telephone business landline but if not then you should reclaim business call costs (and you enter them on your P11D).
It is best to organise a contract for a mobile phone in the company name (one per worker). That way your company pays for personal as well as business calls, which is acceptable to HMRC. Please note that the same concession does not apply to a device such as an iPhone or BlackBerry although if it is provided solely for business use and any private use is not significant, it will be exempt.
Note that dfor your company to pay, mobile phone contracts should be in the company’s name (if not you enter the amount you have claimed from your company on your P11D and look into changing mobile contracts).