Creeping bellflower is the Magpie of the weed world. Pretty to look at, but invasive and annoying as hell
It’s very difficult to get rid of, but as
@potatopizzafan mentioned, getting the roots out is the only way to control it.
Even then, it will still come back, and you will need to be vigilant by pulling it every year, but the more roots you can pull the less you’ll have to deal with the rest if the summer.
Some places are going to be difficult to dig it with a shovel, if it is integrated with or next to existing shrubs or flowers. In that case I would recommend that you soak the area to loosen the soil and come back in 20 minutes and gently pull the bellflower leaves out, Quite often you can get a fair bit of the root out if you do it that way.
Another thing that sometimes works over fairly large areas where you can’t dig is to cover with decorative gravel (large) or large pieces of bark mulch. The larger the pieces the less dense the Bellflower leaves are and the ones that do come through are a bit bigger and thicker making them easier to pull.
