Replacement Formula Required In Excel

Hello,


I have an excel sheet containing many phone numbers in a column, but the problem is that in some cells containing two phone numbers and those are separated by "/" (please read that without ")

First Requirement:
Now I want a formula by which I can insert the same data of a particular row to the next row.

Second Requirement:
Say it is like

123456781/123
or
123456781/1
or
123456781/99

Now if there are two digits after the "/" I want to replace those two digits with previous digits before "/"

i.e. 21212121212/33

I want 21212121233

Please help me.

Regards,

plagha