how to update my phone # on my hotmail account?

My account has been hacked and i just got the password recovered.  The hacker will probably get it changed again as the phone number is wrong on my account.  How can i update my phone # on my account so that they don't get back in again?  Is there a possibility that they are in my pc and searching everything else in there?  I called Microsoft support ( a # I got off google.ca) and they said it is being used in the Phillipines and Microsoft needs a technician to go online via  remote access to remove the hacker information.  I didn't feel comfortable with him doing that so I ended my call.  Pls HELP I am feeling helpless and very concerned with my personal information being invaded.  Thank you.