If they don't stop after registering with the TPS and asking them to stop, report them to the Information Commissioner
https://ico.org.uk/concerns/marketing/
Helps if you have the times of the calls and numbers; do mention you feel 'harrassed' as then they have to take action. Worked for me with one company. The ICO's powers are going to increase to make it easier prosecute companies, long overdue.
http://www.mirror.co.uk/news/uk-news...isance-5225768