Not as professional advice or opinion:
My doctor goes by what the patient says.
He says he has seen plenty of dipstick negative urine tests come back positive for UTI.
The fact that you have needed to increase your pump's basal rate is pretty suggestive too.
Tell them you have a UTI until proven otherwise - that means a urine M/C/S please and pre-emptive antibiotic treatment because they have delayed your diagnosis and treatment and and you need to get things back to normal.
Or the doc has to spend more time trying to sort out more obscure (ones that are not obvious) causes for your raised insulin requirement and pretty conclusive of UTI symptoms !!
Best Wishes.
In Oz we can be forthright when needed, but politefully jovial when relaxed and all is well.