Okay, this is definitely in the quick and dirty school of IT Engineering but we've all done it and, actually, Excel is mega handy for this. I do agree with @Pauska that Powershell and CSV's are the way forwards, though.
Anyway, the quickest and easiest way to do this (For a one off job, anyway) is to organise your excel sheet as follows:
Cell A Cell B Cell C
+------------+------------+------------+
1 + Username + Telephone + Fax +
+------------+------------+------------+
2 + User1 +123456789012+987643210987+
And so on. Then, in column D, on Row 2 create a formula that uses concatenation to build your individual command line, ending with something along these lines:
="dsquery user -samid '" & A2 & "' 'OU=Sys,OU=Prod Services,DC=win,DC=ite,DC=com' | dsmod user -mobile '" & B2 & "'"
You can then select that whole column, copy and paste it notepad and voila - a batch file which will do what you need.