Harassment

This company has been phoning me for months, looking for a M Dhaka. I have emailed, and told them numerous times that I do not know such a person, and that they can even check my Rica details, the phone number has been registered in my name for the past 6 years already. They phone at least 4 times a week. I block the number, they use another one. This is seriously bordering on harassment. I have been rude, I have been patient, I have explained numerous times. They still phone me. I am starting to contemplate legal action against the constant phone calls