Debt collector chasing a current account debt

[karlsen1]

My defaulted Halifax current account debt now about £1200 (which was actually £900) has be 'transferred' to Crapquest and they keep ringing my home phone every day leaving a recorded message to contract them and also the same on my mobile phone. I did try to get Halifax to freeze the debt as they were adding charges of £5 each day interest charges due to financial hardship
What can I do as I certainly did try to sort out the problem with Halifax but they would not agree to freeze the debt ?
Any help would be greatly appreciated.
Many thanks