Drop calls, only works in certian area

Drop calls, only works in certian area. would like to send it back and get a diffrent phone. Feel as if I just lost money on a bad product. It works but I had to send it back because could not hear on it. you can use your sim if it fits. I would not recommend this phone to anyone. this phone is slow. I have problems going on the internet. All kinds of Chinese or Japanese apps pop up on there own. oppo find 5  They give you two battery and you will need them. Now it hard for it to charged. I am getting a new phone this. One really sucks. I don't have s clue of any warranty .
This item has a slot for micro SIM card as well as one for standard SIM card. You can just install an active/existing GSM network SIM card [such as AT&T], power on the device, and it should detect the network signal for use within a few moments. If unable to receive MMS or data connection initially, you may have to set up APN prior which we can assist with. This item's warranty is only in case of manufacturer's defects [i.e. defective soundcard, display, etc.] it does not cover physical damage...physical damage to the item [i.e. cracked screen or water damage, etc.] will void and null the manufacturer's warranty. I hope this helped to answer your questions and please let us know if you should have any additional questions.
I like the design, very thin and has big screen clear and sharp the camera is good but do not have enough internal memory to store my picture and music...Need to use my own micro sd card...overall a good smartphone for the price.It shuts down, to slow to even use any apps.