Many thanks for your patience. The problem here is that you have been specifically sked not to contact the old employer and if you do so, even with the intention of trying to resolve this, then you could be creating more issues for yourself. If they are unwilling to talk with you about it you cannot force them unfortunately. However, if you are adamant that you have not stolen anything from them and they have no evidence to back that up, you could consider telling them that this amounts to potential defamation.
First of all, certain conditions must be met for the statement to be classified as defamatory. These are:
1. The statement has to be untrue.
2. It must directly identify the complainant.
3. It must have been published, usually communicated to at least another person.
4. It must be in a form of words, which would tend to lower the claimant in the estimation of ‘right thinking members of society generally', expose the claimant to hatred, contempt or ridicule, or cause the claimant to be shunned or avoided.
5. Its publication has caused or is likely to cause serious harm to the reputation of the claimant.
Whilst a claim for this s unrealistic as it is very complex and expensive, there is of course nothing stopping you from contacting the other party and threatening them that what they have done amounts to defamation and that you will consider pursuing the matter further if they do not retract their statement. This could prompt them to reconsider their position. I would suggest you ask the police for permission to contact them about this first so you do not break the request of no contact.
In the meantime keep your current employer up to date so that they do not think you are hiding anything and jeopardise the trust with them.
I hope this has answered your query. I would be grateful if you could please take a second to leave a positive rating by selecting 3, 4 or 5 stars - this is an important part of our process and recognises the time I have spent assisting you. If you still need me to clarify anything else, please get back to me on here and I will assist further as best as I can. Thank you