Getting phone calls when I only provided by email address

I've been looking at quotes for various things about moving house and something I've never experienced before has been happening.

When I go on these quote comparison sites, I enter "0000" for my phone number. I provided my email address though.

However, after getting the quotes, one company managed to call me. When I asked how they got my number, they claimed I entered it when I was searching for quotes which I didn't.

I then searched for a quote …

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