Bad customer service

My mom took her phone to pep in Vaal mall early December for repairs, when she went and check January they said it's not back yet. She went to check today and they said it seems like it's lost, they will give her another phone. My problem is that they don't even call, sms if she did not go there she wouldn't have got the phone, another problem they said she must pay the difference because now is not the same price, I want to know why because she took the same phone, they must give her with the same price, because it's not like they are doing her a favor.it was the manager and the cashier malume and Gladys.she even called me to ask if she did the right thing, because she saw it doesn't look right. Please I want to know how you guys work.