In Cantonese, you often say 轉行 (zyun3 hong4) to say "switch industries". What's the Mandarin equivalent?
转行 is also acceptable in Mandarin. Here's a dictionary entry indicating that it's an alternative to 改行:
◎ 转行 zhuǎnháng
[change one’s profession] 改行
If you search for 转行 you will also find many non-Cantonese-specific results, like this: https://baike.baidu.com/item/%E8%BD%AC%E8%A1%8C