Risk of phone data getting stolen in a repair shop?

So this happen several years ago, my iPhone 7 Plus had a issue (it was stuck in a loop on boot screen). I try to fix it through restoring through iTunes, but it just came up with errors, thus I finally cave in and decided to send it to a repair shop. The repair shop asked me to remove my phone from my iCloud account, which I stupidly decided to do so. A couple weeks later, they couldn’t fixed it …

boot data errors fix iphone issue itunes loop phone privacy repair risk screen send shop stolen