just keep adding soil until you like it that way. no problem for the plant to get more soil. I bury my plants as deep as possible outdoors.

If the old root ball is higher than the new soil, then add soil up to the old level. Otherwise I would only add enough soil to keep your roots covered. If you plan on overwintering again, add more soil next spring by removing the plant from the pot and adding new soil in the bottom of the pot. Or wait until spring and re-pot into a bigger pot again.