Are you following the sign up links before depositing?
This sheet may help >> https://profitkings.wpengine.com/bookmakers-index/
You are from SA which is a bit of a pain. I do know some are still possible to get.
And you can call up straight after depositing tbh when it comes to the first sign up bonuses. Follow the script from Bonus Basher ebook. If it was a promotion payout issue, i would not be calling.