ATM Sangla by a common citizen, excessive interest

Hi!
I'm Rusty,I borrowed P10,000 from a Loaner (locally known as 5'6)...I sign in a piece of paper indicating the amount P10,000 with a 5% interest/month (May to September). I wasn't able to pay the loan until September because I lost my job and now the loaner is harassing me. I'm planning to settle the loan plus interest on October 2, 2010.

I was surprised when she told me that I owe her P29,000.

I was just wondering if the interest rate is legal? is it really
possible that my loan became P29,000 from a small amount of P10k only? I am willing to pay my debt but Im just waiting until my finances are stable coz I just got back from work. If the loaner will insist the unimaginable computation of the loan, Can I file a civil case? please I really need your help...

additional info: the contract is just a small piece of paper that I signed. It's just indicated there the capital of P10k and interest of 5%/mo. , according to her the 10k loan became P29,000+ because of so many additional charges like compound interest etc. But all these hidden charges and interest were not indicated on the contract nor a Terms and Conditions wasn't noted there. There wasn't even a verbal agreement about these hidden interest in the event of failure to pay. She did not provide me copy of my contract and didn't explain her hidden agenda. She's threatening me about filing a lawsuit,is it really possible? does it have a bearing? plus she's harassing me and my family in TEXT msgs (curses, abrasive words, etc.)

what shall I do?

i believe the contract is valid, but the rate of interest is unconscionable and should be reduced equitably. you can offer to pay her at a reduced amount of what you believe is reasonable.

you can consider filing a case of unjust vexation for the text messages against her at the bgy of her residence if you both live in the same municipality or city. if not, directly with the prosecutor's office where you live. you can leverage the case to get a good payment plan.

hi po share lang im working in a financing firm before we release the loan we explain the amt that they well get the deductions the interest so on and so fort, and should sign promissory note and disclosure naka note doon if incase they fail to pay there loan me mga penalities at hindi ka naman nila pwede siguro sampahan ng kaso kasi wala ka pinirmahan or dika nag issue ng cheque kasi bangko ang katapat mo dyan. mahirap mag loan pag may pinirmahan kang cheke kasi pag dka naka pay tatalbog mag closed acct sya kaya sisingilin ka ng sangka tutak na interest at pag dka pa nag pay pwede ka nila kasuhan.