how could i use sed in order to replace text from filetobeprocessed.txt, 

which has names, and tel numbers perhaps in it:

```
Name3 john.D
Name6 mary.D
Name7 kelly.O
etc

```

which has text in a per line basis. The text to be found,exists in fileA.txt, and the replacement string, is found in fileB.txt.

for example, fileA.txt

may have 

Name3 john.D, 

and fileB.txt
may have 

Person: John Diamen,

so filetobeprocessed.txt should become: 

```
Person: John Diamen
Name6 mary.D
Name7 kelly.O

```

Of course, since file to be processed, fileA, and fileB are huge, we may have any character found in the search string, and in the replacement string, so my example is kind of basic, and does not cover all characters that exist in filetobeprocessed.txt
So i need a way, to use sed, to do a search and replace, but do this, for each line found in fileA.txt, and its equivalent string, found in the same number line, in fileB.txt

something with sed -f -

combined with 

```
sed -i 's/old/new/g'

```

or

sed 's/\string to be replaced\b/replacement string/g' file.xml

what i cannot find, is a way to use this for each line of the fileA.txt, which has all strings to be searched for, and for each corresponding replacement line, found in fileB.txt