PBX features / Research What’s the cost of calling 0844, 0845 or 0870 from a Mobile? One of the questions we get asked all the time by startups is “which type of number is best for my business”. There’s no straight answer to this, it depends on your particular needs. One factor to consider is how much will mobile callers need to pay when reaching your business. This can be tricky information to find as mobile operators often have multiple plans and it can depend on the callers contract started.