Unauthorised absence lead to termination of employment

I received today the documents stating the termination of my employment which i didnt sign.Termination is granted after such absence is incurred and considered unauthorized. The company policy is for all employees to call supervisor to notify absence. In my case i was not able to make a call because my cell phone was defective and it could not stay on even for a few minutes. I was absent because as a single parent i cannot leave my child and nephew at home without anyone to look after them. I was able to send a text message to my supervisor informing her of my current condition however management is persistent in not accepting the text message as means of notification and it was considered as my third offense of unauthorised absence.