If you are using a home or mobile phone line for both business and personal calls then you cannot claim for line rental, because there is a dual purpose, i.e. not exclusively for business purposes.
However, you may claim expenses for the business phone calls used on that line. Alternatively, you could set up a separate line in the companys name for business purposes only and charge line rental. If personal calls are used on this line the company will incur a benefit in kind and you will be taxed accordingly.
Your business can provide a mobile phone for work use and any personal calls do not need to be recorded as benefits. With regards to the internet, if the rental is set up in the companys name and there is no significant personal use then there are no taxable benefits. However, if the line is set up under your personal name then you can only charge a portion of the cost to business use.