Why I cannot update payment method
iPhone 13 Pro Max, 15
Question marked as
Try first to optimize the range of the mobile network, see this Apple article:
If you see No Service or Searching on your iPhone or iPad
If you see No Service or Searching on your iPhone or iPad - Apple Support
Optimize the Wi-Fi connection, see the following Apple articles:
Connect to Wi-Fi on your iPhone, iPad, or iPod touch
Connect to Wi-Fi on your iPhone, iPad, or iPod touch - Apple Support
If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network
If your iPhone, iPad, or iPod touch won't connect to a Wi-Fi network - Apple Support
Recommended settings for Wi-Fi routers and access points
Recommended settings for Wi-Fi routers and access points - Apple Support
If you need help with your Wi‑Fi password
If you need help with your Wi‑Fi password - Apple Support
Why I cannot update payment method
Sign in to your Apple ID account page and edit / update your Apple ID details.
On the Sidebar click Payment methods -> then tap Payments Methods and tap Manage payment method.
Or -> Change, add or remove Apple ID payment methods
Change, add or remove Apple ID payment methods – Apple Support (UK)
See also -> About billing for Apple subscriptions and media products in India
About billing for Apple subscriptions and media products in India - Apple Support
India
• Apple ID balance (from adding funds)
• Net Banking (adding funds only)
• UPI (adding funds only)
You can use / pay with your Apple ID balance, see the following Apple articles:
Add money to your Apple ID balance