If your deposit is protected with TDS Insured, your landlord or agent holds your deposit. You should contact them requesting the deposit as soon as possible after your tenancy ends. You only need to contact TDS if you have a dispute with your landlord over deductions from your deposit.
If your deposit is protected with TDS Custodial, TDS will hold your deposit and you must enter a repayment request through your online account after the end of the tenancy.
If you are not sure who holds the deposit, check the tenancy agreement and the prescribed information you received at the start of the tenancy.