ive just this second got a phone call from them, some american guy asking my details,(only got my new phone yesterday) i do not have any debt and they would not disclose who they were to me

Okay MCS are NOT allowed to harass you. You will probably find they are auto dialling you from possible India. MCS is part of HSBC, as in their collection service arm. Do NOT be intimidated by these people and give them as good as you get. If you get hassled note down their call times. Complain to the Financial Ombudsman Service (FOS) and explain the problem. Be assured they will not trouble you if you provide evidence. If you can record rude calls do that too.

just started calling me and I know exactly why - thats not the issue.
The amount of calls I am likely to receive could be though - my advice - enlighten them with the fact they are breaking section 40 of the Administration of Justice act, and you deem the calls to be of a harassing nature. The law does not allow them to harass you in this way - so MCS are breaking the law until the point they realise you know it. They work on the basis you won't know that little piece of information. I might take one call, but the moment I get alot, and they get aggresive I will advise them of this fact in a polite tone and refer them to trading standards.
F**k em

Go to the Citizens Advice Bureau and tell them what's happened.

I had 10 calls today and just got of the phone to them.I got made redundant 2 months ago and had to reduce my monthly payments. Due to the postal strike I have faxed through all my documents as as advised including all letters from DWP and CCCS...STILL I get demands & threats to make large payments even after everything I have provided. These people seriously stress me out as they just dont listen at all. 1 confirms they have had faxes the other knows nothing about it. I just told the last caller to F**K **F as I have been very patient & tolerant with their attitude and manners and the last caller just plain ignored everything I said and demanded a payment.There must be something you can do to stop this harrassement???

As with all debts you should always find out if the creditor or debt collection agency has the legal right to enforce your credit agreement. 80% of credit card agreements taken out before April 2007 are thought to be unenforceable under the Consumer Credit Act. Google “unenforceable credit agreements” for more information. Get free advice from the consumer action forum or the penalty charges forum.