Counting matches in a self-join

The first thing to notice is that your sample results do not match your sample data. Second is that you're apparently counting the matches twice.

Now, counting the matches twice is actually not a bad idea, since that makes it much easier to look up any given tapeid to find out its matches. So here's the query to do that:

select a.tapeid
     , b.tapeid as matchingid
     , count(*) as matches
  from yourtable as a
inner
  join yourtable as b
    on a.phonenumber = b.phonenumber  
   and a.tapeid <> b.tapeid
group 
    by a.tapeid
     , b.tapeid   
order 
    by a.tapeid
     , b.tapeid

The reason for and a.tapeid <> b.tapeid is to exclude counts for tapeids that match themselves (since they all will). If you wanted to count the matches only once, change it to and a.tapeid < b.tapeid.