No, you will not lose your bitcoins.
If you lose your mobile phone, the person cannot send your bitcoins without your 4 digit PIN. Also if he keeps trying your PIN number, your Zebpay app will be locked after 3 wrong attempts.
Once you get a new SIM card, you can reinstall the Zebpay app on the new mobile phone. Once you enter your mobile number and PIN in the Zebpay app, your bitcoins and transaction history will be visible on the new phone.