Just got a HTC Wildfire S with a facebook app, do i still have to pay for facebook?

[Nicolla Everett]

So on friday i bought a pay as you go HTC Wildfire S from tesco (tesco mobile) and it already had a facebook app on it. I connected it with my house's WiFi and it worked fine. I'm not very good at technology and i just assumed that the andriod market, facebook and internet and everything was free because of the wifi. I was texting a lot over the weekend and when i checked my balance it said i had £6.05 of free credit left (i payed £10 of credit and i got £20 free). i couldnt believe how much credit had gone already considering i've only had the phone for two days...so what i'm trying to say is: has all my credit gone because i was using the internet, facebook and android market or was it becasue of my texting. and also; when i use my facebook app do i have to pay or is it free...? Even answering one of these questions would help me a lot! Thanks!! xx