I shall be/would be

Hi there, can anyone please tell me what the difference between two underlined sentence is?

To
The Chief Engineer,
Telephone Bhawan,
Kolkata - 700091

I would like to state that I applied for a new telephone on 05.02.2016. Though more than two years have passed since the application, I have not received the new connection yet nor have I been informed at what stage my application for the connection is at present. Kindly let me know when I can expect the connection.

I shall be grateful if you take immediate steps in this regard./I would be grateful if you would take immediate steps in this regard.

My question is, are both the underlined sentences correct In the above context? If yes, what is the difference berween them?

Thanks in advance.