How long was the contract you signed with them for?
You are contractually bound, unless they agree to let it go (unlikely) or they have breached the contract in some way, to pay up to the end of the contract or they have every rights to pursue you for the remaining unpaid amount.
Are you able to afford it better in the near future as some contracts have a holiday period in where you can suspend the contract for say a couple of months, though this is usually added onto the end but if you have already defaulted on payments then this may not be an option.
Are you able to make some payments as the last thing you need is for them to get debt collectors involved or for them to issue court proceedings as this will only increase the amount owed.
Trouble is, there would be no point in them signing people up to contracts if they could just be got out of easily and they rely on people's own judgement as to whether they can afford to keep it up before they sign.
Obviously some things like losing a job or illness cannot be forseen but they often have the options to opt out for a few months or with a doctors note to help with these kind of situations.