Adjustment of Sign on Bonus returned to Employer in same Financial Year in IT Returns

Hi, I was given a joining bonus of approx 2 lacs when I joined a new company 2 months back. Now I am quitting this job for another one and have been asked to return the amount in full back to the employer, only then they will process my full and final settlement. I have requested them to adjust it in my salary slips so that it is not shown as separate income on my Form-16. Ideally I want my form 16 to include only the salary of 2 months that I worked there and not the joining bonus as that is increasing my tax liability. However, the company is not agreeing to do so and wants to show 2 months salary plus bonus on my Form-16. They are claiming that I can claim refund while filing ITR at the end of the financial year. However my concern is that Form-16 is the proof of my income from that employer, is it legal for me to just change the value while filing IT return? If so, what is the appropriate section to claim this in as deduction? More so, is it legal for the company to show the bonus as my income when I am returning it to them? Please help me understand this at the earliest as my last working day is in a week. What should I do? Thanks