Excel Bulk Duplicate Find and Delete

Hello,

I have large a amount of data and I am having some issues with duplicates within the list. Basically, my list looks like this:

I want to be able to run a macro or write a formula which will look at collumn A and check for duplicates. As you can see in row 3 & 8 have the same mobile number but different people. I want to be able to run the macro so that it will look at all of collumn A and see that number 7700900917 appears twice and delete all of row 3 or 8 leaving one unique record. The reason i am trying to automate this, is because my records are over 800,000 and this will take much time. Also, data is not original data for DPA purposes.