I infer from your second post in this thread that the bank has been writing to you in your capacity as director. Anything written to you in that capacity should be passed to the liquidator, because all directors' powers are now vested in the liquidator.
If the bank writes to you in your capacity as loan guarantor, then it's a different problem. How it should be handled depends on the particular circumstances, but I think it would almost certainly make sense to discuss the matter with the liquidator. You would need to clarify how much, if any, of your personal guarantee might be called on (you do seem to think that the full amount will be required, and I suppose that you have a good idea of the facts).
Don't get hung up on the question of resigning your directorship: it's not really an issue.