Payment of relocation

Hi,
I was an employee of company "A" and working in company "B" as a temp employee for 8 months. Company "B" has hired me and now I am joining a company "B". Before joining company "A", HR from company "A" promised me to "X" base salary , "Y" bonus and "Z" yearend bonus. "Y" bonus had been paid to me in 12 equal installments i.e. one installment per month. In the offer letter, it was mentioned that if I leave the company before one year, I have to return bonus (Y + Z) plus relocation amount ("W").
After joining the company, they asked me to sign one letter where both these bonus has been converted to retention bonus. I mean, if I do not stay for 1 year, I have to return all the amount of "Y", which I have got and I will not get amount "Z". In this situation, do I need to pay relocation amount as it is case of roll over ? Can it be pro rata base ?

Exact statement in my offer letter was as below.
"In case of voluntary termination within first 12 months of joining A , travel expenses, bonus and any special allowances paid by the company shall be refunded by you"
Here "refund" will be considered as 100% repayment or partial repayment ?