Resigned employee not getting Annual increment Letter

I resigned my job on May 10, 2024. To my surprise I have not got my Annual increment letter. When I asked my HR BP, he mentioned like resigned employees will not be entitled for the letter. I can’t understand the fact behind this. All the effort that has been put and got a B Band into I feel it is waste. I don’t expect this from TCS.. what is the management going to get by doing such things. I am not sure I can sue Tcs for this. Suggestions are welcome