On bluetooth call ( air podspro ) prevents wifi from connecting to router ; iphone 13 ( ios 15.3.1) connects to wifi once bluetooth is turned off

Arul Prasanna,

Thanks for getting back in touch with us. 

Does the same thing happen if you connect your iPhone to a 5GHz band? Here are our recommendations to ensure a reliable Wi-Fi connection:

Recommended settings for Wi-Fi routers and access points

Did you also have a chance to complete the steps we’ve advised above? Ensuring that your iPhone is in range of the router, checking for issues with the network, restarting your devices, and resetting the network settings might help.

Additionally, if you notice this same behavior when your AirPods are paired to another device, try resetting them. Here's how:

How to reset your AirPods and AirPods Pro

If each of those steps didn't resolve the issue, let's also be sure your iPhone is fully updated since fixes are included with each update. If an update is available, we suggest having a current backup to iCloud or to a computer, first.

How to back up your iPhone, iPad, and iPod touch

Update your iPhone, iPad, or iPod touch

Have a great rest of your day or evening.

See this support article→Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support

Also, try with other Wi-Fi routers; the Wi-Fi band and Bluetooth band are pretty close; a router using 2.4 GHz that is mistuned or defective might interfere with Bluetooth that also uses a different part of the 2.4 GHz band (as do microwave ovens, BTW). It is very uncommon, but it can happen.

Hello Arul Prasanna,

Thank you for posting in the Apple Support Communities. We'd like to offer our support for your iPhone 13.

We recommend following the steps in the below support article since they have resolved similar concerns with Wi-Fi in the past:

If your iPhone, iPad, or iPod touch won't connect to a Wi-Fi network

Additionally, connecting your iPhone to another reliable Wi-Fi network, and testing your AirPods Pro with another iOS device may provide you with additional clues.

If the issue continues thereafter, feel free to reply back to this thread with the results after completing each of these steps. The more information you provide, the better chance the community will be able to offer some additional guidance.

Kind regards.

Arul Prasanna,

OK. It sounds like connecting to the 5GHz band works. It's possible that the 2.4GHz band can't support your iPhone when connected via Bluetooth headphones on calls. Reviewing the support article shared earlier, Resolve Wi-Fi and Bluetooth issues caused by wireless interference, may help.

To test the issue further, you might try connecting another iPhone to that band, then making a call using Bluetooth headphones. If the issue can be reproduced with another device, it might point to the network.

If this concern continues, feel free to connect with Apple Support directly. Depending on your region, you may be able to reach them here: 

Get Support

Take care.