Is the Wi-Fi network affecting my cellphone data service (3G or 4G)?
In short, no. It's technically impossible for Wi-Fi to interfere with cellular service, and it's actually illegal for anyone to interfere with cellular transmission. For the tech geeks among us, Wi-Fi and cellular data run on different frequencies, so they don't directly interfere with each other.
Cellular service is also delivered over licensed spectrum, meaning that your service provider owns that specific frequency range, to ensure they can provide service without interference. It is possible for things like Bluetooth and microwaves to interfere with Wi-Fi because they all use the same unlicensed spectrum frequencies. But none of those technologies can interfere with your cellphone internet service.