No feedback about cell phone repair

Im very ****ed with the service I'm getting from pep, i bought my wife a cellphone for her birthday, and since the start it has given her problems, its throws you out of the apps and some apps don't work. Took it back 10days after on the 15th of December, the guy tried to find the problem nut was unsuccessful. They sent the phone for the repairs the 18th of December. I asked for feedback but they said to call the repair company, so i did, they said they could not give me any information and I should go back to pep for information about the phone. So i went back again and still no feedback, they only say come back next week and ehen i do they say come back next week. Its been more than a no feedback, no phone!!! I want answers ASAP