Please go through following steps:
Check Signal Strength: Ensure you have good signal strength (more bars) on your phone. If you are in an area with poor coverage, that could be the issue.
Restart Your Phone: Sometimes, simply restarting your phone can resolve connectivity issues.
Check for Updates: Ensure your iPhone's iOS is up to date. Sometimes, updates include improvements and bug fixes related to connectivity.
Toggle Airplane Mode: Turn on Airplane Mode for about 10 seconds, then turn it off. This can reset your connection to the cellular network.
Reset Network Settings: Go to Settings > General > Reset > Reset Network Settings. Note that this will erase saved Wi-Fi passwords.
Contact Your Carrier: There might be issues with your carrier's network. Contact them to check if there are any known problems or if they have specific settings for your device.
Check Data Plan: Ensure you haven’t reached your data limit, as some carriers throttle speeds after a certain threshold.
Switch to a Different Network Type: Try switching between LTE, 5G, or 3G to see if there’s any improvement. You can do this in Settings > Cellular > Cellular Data Options > Voice & Data.
Remove and Reinsert SIM Card: Sometimes, reseating the SIM card can help.
Disable VPN: If you are using a VPN, try disabling it to see if it improves your speed.
Test in Different Locations: Try using your phone in different locations to see if the issue persists. This can help determine if it's a location-specific problem.
Use Wi-Fi: If available, use Wi-Fi instead of cellular data when you're in a place with a reliable Wi-Fi network.
If none of these steps resolve the issue, it might be a hardware problem with your phone, in which case visiting an Apple Store or an authorized service provider would be advisable.
