Jim's phone number is for general enquiries. (If your query is of a technical nature you won't get support there. Microsoft only provides telephone support to business customers, who have to pay through the nose to get it). The lines are open from 0800 to 1800, Mon to Fri.
A call to an 0344 number is charged at exactly the same rate as to a normal 01 or 02 number. That applies when calling from both landlines and mobiles. Further, if your phone company gives you free calls to 01 and 02 numbers (e.g. as part of the 'included minutes' on a mobile call plan) they must also give you free calls to 03 numbers.
A useful link to bookmark:
http://consumers.ofcom.org.uk/phone/how-much-does-a-phone-call-really-cost/