I guess you checked out the xONEx rules here:
Code:
16. VOLUNTARY CHANGES/REROUTING/PENALTIES
(a) Rebooking/Rerouting
(1) Prior to departure
(a) Origin TC1
(1) Before ticket issuance - Permitted without penalty.
(2) After ticket issuance - Changes to the first international
flight and preceding flights are not permitted less than
seven days prior to the date of the first ticketed flight.
Date/time changes to other flights permitted at no charge.
Date/Time/oneworld Carrier changes are permitted without
reissue provided origin/destination/connecting points and
inventory remain the same.
Changes other than to Date/Time/oneworld carrier permitted
at a charge of USD125.00 per transaction.
...
(b) Cancellations and Refunds
(1) Prior to departure
(a) Origin TC1
(1) Before ticket issuance - full refund
(2) After ticket issuance - 10 percent of ticketed amount
...
(c) Upgrading
(1) An Economy oneworld Explorer fare may be upgraded to a First/
Business class oneworld Explorer fare without penalty.
(2) A Business oneworld Explorer fare may be upgraded to a First
class oneworld Explorer fare without penalty.
(3) Upgrading by sector to Business/First class is not permitted.
(4) At any time the oneworld Explorer fare may be used as credit
towards a full mileage fare or a Global Explorer fare (provided
the conditions of Global Explorer have been met). No penalty
will apply. Reissued tickets must be endorsed
--NON REF/XXX--//XXX equals oneworld Explorer fare basis
code//and the original non-refundable amount remains non-
refundable. If the upgraded ticket is subsequently cancelled
the original penalty will apply.
By the rules:
- 16.(a)(1)(a)(2) prevents changes in the OP's case as it's less than 7 days before departure if the first flight from TC1,
- 16.(C) is probably out of the question (DONE4->AONE4 upgrade is USD3,100 more).
- As Viajero indicated, by the rules, 16.(b)(1)(a)(2) would be your best solution incurring a 10% penalty
Note that it is not relevant that your first international flight is 10+ days away:
... Changes to the first international flight and preceding flights are not permitted less than seven days prior to the date of the first ticketed flight ...