I'll be glad to help. If double lines and ink overflow are still occurring after replacing your Canon toner cartridge, the symptoms indicate either a paper media, cleaning or hardware related issue.
Please ensure that supported paper weights and types are being used (16-60lb. depending on paper tray), and they are loaded properly without overflow.
An issue of double lines or black streaks that are either being produced only when using the Automatic Document Feeder, or with every print, can often be resolved with cleaning. Cleaning the Automatic Document Feeder and/or the Fixing Assembly can help. Clicking the link to select article "Cleaning the Machine" will walk you through the steps as well as cleaning the Platen Glass.
If the issue remains, after the above is performed, please contact us for further assistance.