Try ringing Citizens' Information and ask their advice. Their landline number is 021 4521600 if you don't want to ring the expensive 1890 number. Don't ring the bank until you have their advice.
This key post is relevant although a few years old but may help.
Have you contacted the company itself or just the subcontractor in relation to the second visit? If not the company itself, then you should contact them & report the issues you are experiencing, have all facts at hand, dates, agreements of number of calls, payment etc... If nothing satisfactory from that, then go down the route of charge-back.