How do I request a chargeback related to my Tally Debit Mastercard?

IIn the case of fraudulent activity, merchant disputes, authorisation-related disputes or point of interaction errors, you are protected under the Mastercard chargeback scheme. Customers have 120 days from the date of the transaction to notify Tally and provide details of the incorrect charge. 

In the case of fraudulent activity, we will open the investigation as soon as we receive the claim and, once confirmed, process the refund within 48 hours.
In the case of merchant disputes, merchants have 45 days to respond. If no response is received, the chargeback will be processed as soon as our payment provider has released the funds.
For more information, visit: http://www.theukcardsassociation.org.uk/individual/chargeback-for-credit-and-debit-card-purchases.asp