entering telephone numbers

Hi,

I am inputting a long list of phone numbers and I want to delete the gaps inbetwen them in each cell- for example 796 789 789 to 796789789. I have seen that you can use the substitute or find and replace functions- have tried both- pretty sure I am not entering it correctly! Also if I can then delete the spaces can I then prefix the numbers with a country code rather than having to inout each one by one.

Thanks!

Sorry perhaps this was unclear- the list of telephone numbers I am copying in already has the spaces