Samsung S 5570: I deleted important files and can't send texts.

Basically, i was trying to clear space on my phone as it was very low. There was nothing left to delete as my phone memory has been nearly enpty for months despite me deleting all games and apps, (all photos and music stored on sd) and the phone keeps displaying "internal storage full" (this is slightly off topic but if anyone can help me solve that puzzle i'd be grateful) so with nothing left to delete i went onto my apps and starting clearing data. Now i can no longer text, i don't have credit just now but i should have approx 500 texts so i have obviously deleted something important. I know this because it won't eveb let me text my network which is free. Is there anyway to recover this? Thanks, from Skye.