Who sings "im gonna write what i want u 2 do in a letter" in a heineken commercial?

The song in the Heineken commercial entitled The Switch is called Love Letter and is performed by Clairy Browne and the Bangin’ Rackettes. The nine piece ensemble group formed in 2009 in Melbourne, Australia.

They are currently in the middle of a tour that covers Australia and later Europe. Through September they'll be teaming up with Kira Puru & the Bruise for their Tough Love tour. They'll be at Bigsound, The Bakery Lane in Brisbane on September 12; Transit Bar in Canberra on September 15; and Theatre Royale in Castlemaine on September 21. Sadly, no US cities are currently listed in their tour.

They have one studio album called Baby Caught The Bus which includes the song Love Letter and other ska/R’n’B inspired songs.