Auto fill Form and then auto populate other forms

Auto fill Form and then auto populate other forms

Hi

I have form where for the first call company name and other details are entered. How ever for a follow-up call I want the company field to auto fill and on selection auto populate all the data in rest of the fields and remarks to be appended only. Can any one please help me with this? I have been trying to do it since past week.I have the screen shot attached of the form for ready reference.