Endless harassment

This is harassment. They call continuously (take note I have never dealt with them so I would love to know where they got my number) as soon as you answer, they drop the phone. I am sure they have people chasing a certain number of calls per day. I have blocked their number but somehow they still phone. I have sent an email to ask them to stop calling me … the polite lady apologized and promised to remove my number yet numerous calls every day … this has to stop!