What happens if my Wi-Fi icon on my iphone won't turn on?

Like I have an iphone 4/4s and it has a modem Firmware: 04.10.01
and the Wi-Fi button is just turned off, I'm unable to turn it on, the letters are in grey.
I'm trying to figure whether I can fix this on my own or should i go get help.

If it is grey it is a problem with the motherboard and will be very expensive to repair. Also it is very hard to find a shop that offer this type of repair.

http://ibuybroken.com/

Similarly, my own IPhone 6 did this, I'm not sure if it's the same problem or if it's completely different considering it's far newer, if anyone knows about this please respond.

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