Hello Lakhvinder,
As said by gosho is correct.
The same happened with me. I was Training lead for one company but later they changed their name and nature of work also.
I had their experience letter. I went to them and explained my situtation. They did not have any problem in giving me in writing on their new company letter head, as what my position was previously and that they haev changed their work also.
I attached my previous experience letter along with the letter they gave me with my jobs and responsibilties. I also made sure to give explanation on simple letter to CHC in this regard. If you haev any salary please add that too, if you dnt then do not worry just make sure to write all in the explanation.
Please make sure to collect business card so that if CHC makes verification call to the concerned person , he/she can take care also.
Regards
Wolfy