You have bought a mobile phone in a tax-free shop just a few days ago and it doesn't work properly. Write a letter to the manager to complain about it and ask him to solve the problem.
Dear Sir,
I am writing to express my dissatisfaction with the smartphone purchased in your duty-free store 5 days ago. However, the problems started to appear right after it was in use.
The first malfunction was that I could not install any recommended applications on the phone. Whenever I made an effort, the screen was immediately shut down, and I needed to restart the phone again. Furthermore, even when the instruction booklet shows that the phone can function well in a whole day, but mine required to be charged every 5 hours.
Naturally, I contacted your sales representative to report the above issues. However, he suggested going directly to the Warranty Department of the phone's company to have it repaired myself. You can imagine how upset I felt from learning that and I was disappointed with both your services and products. Therefore, I insist the full refund of $350 as soon as possible.
I believe this matter deserves your prompt attention.
Yours faithfully,