The rolling diameter needs to be kept the same (wheel + tyre - if you increase wheel size, you have to run lower profile tyres to match).
And you also have to get the offset right.
Read up on the "Wheel and Tyre Bible" (it's either linked in a sticky here or you can find it on Google) - it explains everything you need to know.
The tyre place should be paying to fix your car, incidently.
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