Only first letter in the cell of the file.

[perfringo]

I am afraid that when you fix this problem you will encounter several new ones.

You current problem is that name and surname are strings and your write specific characters based on index. Dummy example:

>>> name = 'Joe'                                                                                         
>>> surname = 'Doe'                                                                                      
>>> for a in range(3): 
...     print(name[a] + ', ' + surname[a])
...
J, D
o, o
e, e