'fraid not, mon capitain. It should be: So I shopped around to assure myself that the deal they were offering would ensure me the best insurance cover.

One assures somebody of something or that something is the case.

One ensures that an event will occur.

So, the assistant assured me that we would have enough cover. He convinced me that our cover was sufficient.

The assistant ensured that we would have enough cover. He worked non-stop for forty-eight hours so that our cover would be sufficient.

Bingley

Bingley