Activation Lock is on

I bought my Iphone 4S about 4 years ago at a big phone store. It is in a box sealed. Everything inside is new. They helped me make an account in the unit used an email address (gmail.com not icloud.com). The receipt I got is with handwritting. After 2 years I used without any problems, sunddenly Activation Lock showed. I entered the email address when I set up in the store, It didn’t match. Later I know that the unit is refurbhised. I went to the store I bought, they blamed me that I forgot the password..They dont want to be blamed. I call the call centre in my country (Indonesia), after a looong talking, they cant help me. They connected me to the representation in Malaysia. I spoke to her. She said that she can help if I can provide an original receipt. She want the receipt I have. The store could not help me also. They still blamed me. Please anybody here can tell me what am i supposed to do?