I have 7 years back taxes to file. I want to file 2016 and 2017 to get started. I paid H & R Block to do 2018. Must I pay them to get this accomplished?

[VolvoGirl]

You either have to buy the program for each year from somewhere.  Turbo Tax only goes back 3 years here, https://turbotax.intuit.com/personal-taxes/past-years-products/  

Or go to an Accountant.  Or you can fill out the forms by hand for free.  I can give you links to the blank IRS forms if you have a simple return or find them here,
https://apps.irs.gov/app/picklist/list/priorFormPublication.html