Excel 2007 : Removing Duplicates from an Extremely long list

I hope someone can help with this problem i'm having.

I have been compiling a list of telephone numbers for a friend, which has been compiled from a few different sources, and I am trying to remove all the duplicates.

There is only one Field which is the telephone number.

I have looked online and see there are a number of built in functions which can be used to remove duplicates, but they all seem to be based on the list being in one column, and this is where I am having the issue.

My list contains 220,000 numbers, and the maximum number of rows in Excel is around 65,000. As such my entire list is spread across 4 columns of aprox. 53,000 in each column.

I have tried creating a macro in vba using the countif function to identify duplicates and the find function to find and delete them, but at the speed this is running, it is likely to take a week of constant running to complete, if not longer.

Can anyone suggest a quicker way to remove the duplicates, possibly using the functions already built into Excel for finding duplicates?

Not sure if it is relevant, but the list is not in numerical order and cannot be sorted as the list covers a number of columns, and I only know how to sort the individual columns and not the entire range.

Any advice would be greatly appreciated