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That is a SCAM message. Don't call or pay anybody. First we can reset your iPhone. Press and hold down the Power button and Home button at the same time until it shows the Apple logo (ignore slide to turn off message while holding down the buttons). When you see the Apple logo, release the buttons and let it boot.
Don't open Safari yet. Go to Settings tap Safari and tap Clear History and Website Data button. This will clear it. Check Safari.
If you have any questions or would like any additional information, please don't hesitate to ask.