Samsung — not returning my phone from last 14 days

Address:

Shimla, Himachal Pradesh

sir,
i was using samsung galaxy ace s5830 which i bought on[protected].i was not able to turn on wi-fi.i went to samsung care on[protected] then they told me that they are going to change motherboard and told me to collect the phone before[protected].but now they are not returning my phone either they had misplaced it or lost it somewhere.so please look into this issue otherwise i have to take further steps against you.the bill number is [protected].
service center address
church ritz road,cabin no.302,pc shimla 171001.
contact number [protected].