This is what it says in the 'full fare rules':

PENALTIES

CANCELLATIONS ANY TIME CANCELLATIONS PERMITTED FOR CANCEL/NO-SHOW. WAIVED FOR DEATH OF PASSENGER OR FAMILY MEMBER. CHANGES ANY TIME CHANGES PERMITTED. NOTE - ----TICKET VALIDITY---- TICKET IS VALID FOR 1 YEAR FROM THE ORIGINAL DATE OF ISSUANCE AND TRAVEL MUST COMMENCE WITHIN THIS VALIDITY PERIOD. ONCE TRAVEL HAS COMMENCED THEN ALL TRAVEL MUST BE COMPLETED WITHIN 1 YEAR FROM THE DATE ON WHICH TRAVEL COMMENCED. IF A TICKET IS EXCHANGED OR REISSUED - 1. A WHOLLY UNUSED TICKET MUST BE EXCHANGED WITHIN THE ORIGINAL VALIDITY PERIOD OF 1 YEAR AND WILL BE GIVEN A NEW TICKET ISSUE DATE BASED ON THE DATE OF EXCHANGE. 2. IF TRAVEL HAS COMMENCED THEN THE TICKET MUST BE REISSUED AND ALL TRAVEL COMPLETED WITHIN 1 YEAR FROM THE DATE ON WHICH TRAVEL COMMENCED. . -FOR INFORMATION ON TICKET REISSUE PROCEDURES SEE DELTA/S INTERNATIONAL CONTRACT OF CARRIAGE RULE 22 REROUTING

VOLUNTARY CHANGES

IN THE EVENT OF CHANGES TO TICKETED FLIGHTS BEFORE DEPARTURE OF JOURNEY - APPLIES WITHIN TKT VALIDITY CERTAIN DOMESTIC REISSUE PROVISIONS MAY BE OVERRIDDEN BY THOSE OF DL INTERNATIONAL FARES NO CHARGE FOR REISSUE OR HIGHEST FEE OF ALL CHANGED FARE COMPONENTS - CATEGORY 19 DISCOUNTS APPLY AND REPRICE USING FARES IN EFFECT TODAY PROVIDED ALL OF THE FOLLOWING CONDITIONS ARE MET- 1. WHEN NO INTL COUPONS REMAIN - ALL NEW TRAVEL MUST BE DOMESTIC 2. AF/AZ/DL/KL FARES ARE USED 3. ADV RES IS MEASURED FROM REISSUE DATE TO DEPARTURE OF PRICING UNIT OR - REPRICE USING CURRENT FARES - ONLY BOOKING CODE CHANGES PERMITTED PROVIDED ALL OF THE FOLLOWING CONDITIONS ARE MET- 1. NO CHANGE TO FARE BREAKS 2. WHEN NO INTL COUPONS REMAIN - ALL NEW TRAVEL MUST BE DOMESTIC 3. SAME TRAVEL DATES 4. AF/AZ/DL/KL FARES ARE USED 5. ADV RES IS MEASURED FROM REISSUE DATE TO DEPARTURE OF JOURNEY WHEN CHANGE RESULTS IN LOWER FARE SUBTRACT RESIDUAL FROM THE PENALTY THEN ADD-COLLECT/REFUND - REFUND VIA ORIGINAL FORM OF PAYMENT ENDORSEMENT BOX- HIGHER NON-REF AMT AND NEW ENDORSEMENTS. OR - AFTER DEPARTURE OF JOURNEY - APPLIES WITHIN TKT VALIDITY CERTAIN DOMESTIC REISSUE PROVISIONS MAY BE OVERRIDDEN BY THOSE OF DL INTERNATIONAL FARES NO CHARGE FOR REISSUE OR HIGHEST FEE OF ALL CHANGED FARE COMPONENTS - CATEGORY 19 DISCOUNTS APPLY AND REPRICE USING FARES IN EFFECT WHEN TKT WAS ISSUED PROVIDED ALL OF THE FOLLOWING CONDITIONS ARE MET- 1. NO CHANGE TO 1ST FARE COMPONENT 2. WHEN NO INTL COUPONS REMAIN - ALL NEW TRAVEL MUST BE DOMESTIC 3. FULLY FLOWN FARE NOT REPRICED TO FURTHER POINT 4. AF/AM/DL/KE/KL/VA/VS ANY FARE TYPE EXCEPT ERU/EOU/ PRU/ERH ARE USED 5. WHEN SAME FARE USED - ALL RULE AND BOOKING CODE PROVISIONS ARE MET EXCEPT ACCOMPANIED TRAVEL - OTHERWISE ALL PROVISIONS MUST BE MET 6. ADV RES IS MEASURED FROM ORIGINAL TKT DATE TO DEPARTURE OF PRICING UNIT REFUND VIA ORIGINAL FORM OF PAYMENT ENDORSEMENT BOX- HIGHER NON-REF AMT AND NEW ENDORSEMENTS.

I don't quite understand from this if there is a fee or not..