using blitz.gg will result in a ban？

Hello Tavashinho,

First off, let me start by saying welcome to EA’s “Answer HQ”.
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Yeah, there is this notice:

https://support.blitz.gg/hc/en-us/articles/6066587189775-Compliance-with-Rules-and-Regulations-for-Apex-Legends

However, here at AHQ forum we have received several reports regarding the ban & other issues with using Blitz.gg.
Also, I haven't noticed any actual, official EA response confirming that Blitz.gg is allowed. IMO that means such confirmation from EA side does not exist. You use it at your own risk!