Daily harassment

I am being called daily to tell my that I need to make arrangements to pay my account. I have an arrangement in place and I still receive calls daily. The first call is from a private number followed by an 087 number. I have set my phone to harassment filter to block the calls. They cal up to five times daily including weekends and I have given answering the calls. They have now started calling me at work. This is unacceptable. Anywhere they get hold of a number you enter online, the next time you get a call on that number is from Norman Bisset. I pay every month without fail and to be harassed like this by a law firm is beyond comprehension. Should they continue down this path, I will seek legal advice against them.