Agreement by email. Urgent pleas help

I have an unpaid credit card. I stopped paying since 2014 due to financial difficulties. I just got a text message from Panlilio Credit Collections and they said they are going to file a case against me for malicious disregard of something.. I forgot what she said, i deleted the message.. malicious na pagiwas sa pagbabayad ng credit card, something like that. I think they texted me that cause ive been ignoring their text messages and calls for quite sometime now. But that last message scared me so i sent them an email and we decided to enter and agreement. They discounted my balance and agreed to pay the discounted amount on friday (agust12). She sent me the agreement letter stating that i will pay the discounted amount on friday through email, she asked me to sign it and scan it then send it back through email. My question is Can an E-mail Agreement Be a Binding Contract in the philippines? anyway i did what they told me. I just thought What if they edit the amount or date? I asked if they can send me a real Letter thru mail but they said that the deadline is near and i might get the mail late next week if ill wait for it. What are your thoughts on this? Im not sure what im doing please help