How to assign a character string to a number, using information based on a "codebook" in R

Question

Complete R noob here so I would appreciate any help that I can get. I currently have a dataframe that looks something like this:

   NUMBER  RESULT
0     1     2
1     2     4
2     3     6
3     4     8
4     5    10
5     6    12

I have another excel file that functions like a codebook, correspond each specific "NUMBER" to a Name. It looks something like this:

   NUMBER  NAME
0     1    PETER
1     2    SIMON
2     3    STEPHEN
3     4    DOUGLAS
4     5    ADRIAN
5     6    THOMAS

I have about 1000 numbers with 1000 corresponding names. Is there a way I could set 1 = PETER, 2 = SIMON ... etc, so I would be able to match each "NUMBER" with the corresponding "NAME" create a dataframe that looks like this?

   NUMBER  RESULTS   NAME   
0     1     2        PETER
1     2     4        SIMON
2     3     6        STEPHEN
3     4     8        DOUGLAS
4     5    10        ADRIAN
5     6    12        THOMAS 

I have tried using the match function, but have not been successful in my pursuit. Any help would be really appreciated! Thank you!