Harassing phone calls

After receiving a call from them about an offer, I declined it. After declining, they still proceeded to call me consecutively. I had blocked their number as I made it clear I am not interested in what they have to offer. Since blocking the number on the 11th of April 2024, they have called me 35 times. If this does not stop after I tell them once more to stop calling me I'm going to take legal action as this is now harassment.