I got a question in smart site that i cant understand?

i want to used facebook unlimited in just one day" i thought that theres a php 20 only pesos" plss tell me? i wish that for only have 20 pesos i have a unlimited facebook in smart for my phone? my phone unit is 6280 and my # is 09499366979"..theres vailable in smart like this?? plss tell me?..