My iPhone 5s always (since I bought it 14 months ago) connected to my Wi-Fi at home in priority over the 3G or 4G connection. Recently (for about 2 weeks now) it gives preference to 4G for some reason and my mobile internet service limit (200 MB) goes over in a few minutes if I'm watching a video, for example.

Why would this happen?

I don't remember changing anything in the definitions/options, only thing I did was an update to a new version of iOS, but then it only started to happen about 3 weeks after I did that update, so it seems like it's not related with that.

Can I do anything to stop this from happening?

Is it possible that I'm getting cuts in my wifi service and while the phone does not get connection with the Wi-Fi it starts to get it from the 4G connection without asking or even letting me know?

  • ordinarily, it would only switch over to 4G if it lost the wifi signal completely. It should cling onto the wifi even if your ISP connection goes down, so long as the wifi is still up.
    – Tetsujin
    Apr 2, 2015 at 11:21
  • It is not clear from your question whether iPhone switches to 4G (showing its icon on the upper bar), or still shows it's connected to WiFi but uses cellular data.
    – zerohedge
    Apr 2, 2015 at 11:42
  • Also, are you an AT&T customer?
    – zerohedge
    Apr 2, 2015 at 11:54

2 Answers 2


You should check on the WiFi Assist feature of iOS 9 here. It's on by default, and many have complained about it.

Turn Wi-Fi Assist on or off

Wi-Fi Assist is on by default. If you don't want your iOS device to stay connected to the Internet when you have a poor Wi-Fi connection, you can disable Wi-Fi Assist. Go to Settings > Cellular. Then scroll down and tap Wi-Fi Assist.


Try the following, in this order:

  1. Select your network, "Forget", and then re-authenticate.
  2. Settings > General > Reset > Reset Network Settings (NOT ALL SETTINGS)

If this doesn't solve your problem, and if the issue is that the WiFi icon is showing up, but cellular data is still being consumed, try to go to the analytics and usage settings. Examples:

  • Turn off background app refresh
  • Turn off specific apps from using cellular data

There have been some issues in the past where iDevices would disconnect from WiFi upon sleep/screen lock, and cellular data would be consumed with these auto updating features working in the background at the same time.

  • Thanks both! zerohedge: I'll try that and I'll come back here in about 12h-48h and let you know. Regarding your question, I think it still shows it's connected to WiFi while using cellular data, but I'm not totally sure. And no AT&T customer (if you mean the company named AT&T). I'm actually in Europe. I'm getting connection failures from my wifi source at home, like it stops for 1 minute every 5 minutes, so I'm really starting to think that the phone turns automatically to 4G when it detects that the wifi is not "working". But I'll try what you suggested and I'll let you know. Thanks a lot!
    – p_Lopez
    Apr 2, 2015 at 13:55

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .