Promotion advertising error

 I upgraded my phone through an Xfinity promotion that advertised the iPhone 17 for $19.44 per month for 36 months. This price was supposed to include an $11.11 monthly discount, but my bill shows the full charge of $30.55. When I called customer service, they confirmed the $11.11 discount shouldn’t apply. Being promised a promotional price of $19.44 only to be charged the full $30.55 feels like a bait-and-switch. Please adjust my bill and apply the correct promotional pricing.