Are these sentences correct?

As you will recall, he has availed 2 travel fare when his last vacation in June 2014, so he has decided to utilize one and other one for encashment, but you have paid him the encashment only $ 800 for travel fare for the period of July 2013 to July 2014 because it was not due when he was taken in June 2014. It was agreed that the difference will be paid / pay back, based on the fare in July 2014.The air fare in July was $1200, so please arrange to pay this shortfall / deference at the earliest.