Switch to Xfinity Mobile and you'll be able to take $400 off any Samsung Galaxy Phone, including the new Samsung Galaxy S21 5G. You'll need to open a new line and transfer your number to Xfinity Mobile in order to claim the monthly credit. With the discount, the Samsung Galaxy S21 5G drops to $16.67 per month for 24 months, which brings its total price to $400 and makes it the best price we found for the phone with any carrier by $300. Plans start at just $15 per month for 1GB of 5G data. An Unlimited plan is also available for $45 per month. Shipping is free. Sales tax is charged in most state.