You do not have to use Sprintax to prepare form 1040NR. You can use any tools or even IRS website to locate the form https://www.irs.gov/pub/irs-pdf/f1040nr.pdf. When you do the amendment form 1040-X ( see above answer) , that's how IRS know you are correcting your original return. Therefore, you do not need to contact them separately.
