collections payment

thank you atty. another question if you don't mind. they are forcing me to pay on the third of july which is like 3 days from today. I stated that I can make my usual payment of 3000php on the 15th which is my next payday. but he is insisting of a 10k payment on the 3rd of july. and that I should fax a promissory note that I'm making a payment of that amt. should I just ignore the promissory note they're asking and just make my payment on the 15th for the usual amt? what if they file the case before the 15th? thing is I already showed my intentions of paying them the usual amt on the 15th and so on. and also why are they stating a very huge amt almost doubling the amt. I loaned? I made a lot of payments before. Is it legal for them to continuously add fees on top of it? isn't there a limit for maximum fees to be added? can I question that too as well atty.? pls.advise me of what would be the best option atty. with regards to this matter.thank you, more power, God bless!