2019 RAM 1500 Speedometer Reset or Correction

[Gumbo]

Good afternoon all. My wife has a 2019 RAM 1500 with the 5.7 Hemi. It came with 285/45R22XL tires, being a low profile tire she did not like the looks or ride, we changed them to LT275/65R20 at first tire purchase. Of course that threw the speedometer off. At 45 mph actual is 48 mph, 50 mph actual is 54 mph, 55 mph actual is 60 mph, 70 mph actual is 76 mph, and 75 mph actual is 81 - 82 mph. I decided I wanted to get the speedometer reset to read correctly. The local Dodge dealer says you cannot change the setting in anyway to correct the tire size. Our local dealer’s “technicians” and service department leave much to be desired in service and knowledge, so my question here is, is this true or can a 2019 RAM’s speedometer be adjusted or reset? Thank you for you time and knowledge.