So which api or url can i use without ban issue?
Hmm, to be honest, any free service won't assist you after a while. You should consider temporary anything that is free. Would you find it better if you ran your own node just for the mempool?
I have been making a few tests recently in a new project, and even in my old portal i have never faced ban issues in free api.
Most of those exchanges and blockexplorers API have very big limits, such as more than 1 per minute.
He has facing issues because he was basically attacking websites, refreshing webpages that were not created for that purpose. Using free API is totally fine based in my experience.
For example, blockchair API have a limit of 1440 requests per day for free:
https://blockchair.com/api/docs#link_M05