Hi,
You have refused the offer by new company to stay with your current organisation based on the assurance of increment. But your current organisation is living to their words.
now answering to your query,
Write back to your current organisation/ authorised person who has committed your increment citing all the details which you have shared in the mail.
Mention that since you have not been paid as per the commitment by the organisation to consider, ask them your earlier resignation date and also state your Last working day clearly in the mail.
They may not accept, but to have clean exit, you have to keep your communication clear and intact.