Just off the top of my head, I would go with something similar to:
1. On a scale of 1-5, with 1 being "Very Poor", 2 being "Poor", 3 being "Average", 4 being "Good" and 5 being "Very Good", how would you rate your devices performance during your stay with us?
2. Did you experience any interruptions in network connectivity during your time with us? (Yes/No)
3. Were you unable to browse, view, download, load, or upload anything during your time with us? (Yes/No)
4. Have you experienced any issues while using other networks recently (within the last 2 weeks)? (Yes/No) [This would let you know if there's a possibility issues are occurring because of the client device instead of your network].
5. Do you have any other comments or feedback regarding out network performance during your stay with us? (Text field)