fast charging not working

my s6 edge is few months old
but the fast charging doesnt seem to work
when i connected the charger it did get detect as fast charger but immediately it vibrated once or twice & started showing "cable charging"
the charger is fine & i did ensure that the charger is pushed in & connected properly as stated in few threads
nothing seems to work
i used the same charger on my friends s6...
fast charging worked on his phone
then to make sure i used his phone's fast charger & it still shows cable charging
is it related to some rom issue?
cause for some random reason im not getting the 5.1.1 update

ps. warranty/replacement is out of question as it was a gift from one of my relatives. the phone was bought from Singapore