There are a few reasons you may still be receiving calls once signed up.
The first step is to make sure your TPS registration is active, which you can check on the TPS Website.
Make sure it has been 28 days since you registered, as that is the TPS timeline before their protection comes into effect. After that, anyone still calling you with a marketing offer that you have not opted in to is likely to be breaking the law (third paragraph on this page) and is potentially a scam or fraud.
There are a number of ways to protect yourself from this, which we have covered in greater detail here.