Trending @Capgemini; Suggest on Negotiation.

Hi,

I recently interviewed for a company and got the offer letter. Need suggestions on possible options that could've been done and what can be done now.

1. My expectations were 8 fixed lpa but they have offered 6 lpa fixed and 2 lpa variables.
2. I didn't have any other offers at that time so had accepted this offer.
3. Initially when they had released the offer letter,they offered a different location other than my preferred location. But upon a discussion the HR agreed to change it to my preferred location and said that she would release the new offer letter in 10 days. It's been 3 weeks but I'm yet to receive the new offer letter. I've already mailed her 3-4 times and called as well but no reply. Should I escalate her or wait for her to release the new offer?

Also, considering the compensation Should I have done negotiation in the 1st place to change the structure (Atleast 7 fix and 1 var)?

And since i didn't do negotiation at that time is it okay to negotiate now when I have accepted the offer letter? If yes how?