iPhone 14 Pro Max call failure and data issues after iOS26 update

I upgraded my iphone 14 pro max to iOS26 from iOS18.7 and after the update when I try to make a call it shows call failed, and even when I turn on my mobile network in doesn't work. I can't even turn on my hotspot also. I can't use my data to search any browser or anything. I don't know why this is happening. Please what do I do because i cannot connect to the internet except I'm connected to a Wi-Fi but it wasn't like this before the upgrade. Everything has been working perfectly before now. Please how do I fix this

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