This will be my final entry on this matter, the situation has concluded, for those that do wanna know how this turned out i will paraphrase below in bullet points, in terms of the ''aggressive'' stance, i did apologize in all follow up emails to the companies involved, stating it was an emotional reaction to the situation, they all responded that no one in their respective companies took any of that emotion personally and i thanked them for that.
Outcome:
WMT:
1. I accepted WMT offer of full financial reimbursement + a complimentary Day Pass(these tickets used to be sold by London Midland online for 20 pound and could be used in off peak, however these new complimentary tickets have no ticket restrictions in terms of times you can use them).
Chiltern:
1. They took the longest time to respond and investigate, myself and Avanti were already in the middle of the legal arguments and counter arguments before chiltern responded, but nonetheless, they put all the blame on WMT for not calling their control team to accept the endorsement, their staff member didn't do anything wrong, but was to be retrained to do the situation right the next time it happened, they also stated that no TOC can endorse a passenger on another TOC's services.
2. They refunded my ticket despite me calling and given written evidence that this was not an accepted position, which they ignored, but as the tickets were purchased as a gift to myself from a family member, and since they were not the Passenger in this situation, it does not count from a legal perspective as a double claim to the railway and despite me trying to stop and alert Chiltern to this mistake, they ultimately just ignored me and surprisingly haven't tried to reclaim the amount from this family member.
3. They ultimately deadlocked after i called them out on their lie about endorsements not existing by showing them an extract from an email Avanti had sent me stating that chiltern/WMT should have endorsed the ticket.
Avanti:
1. So as others here have said, this conversation was between myself and the customer service agent + their legal team + their managers, ultimately we debated on the position of the situation back and forth and the conditions of the NRCoT in length, we even argued the legal position of: ''Regulation (EC) No 1371/2007 of the European Parliament and of the Council of 23 October 2007 on rail passengers’ rights and obligations also confirms the need for an excess charge under Annex I, TITLE II, Conclusion and Performance of the Contract of Carriage, Article 9''.
2. We reached a stalemate deadlock position, they maintain under condition 13.2 they had the right to charge me the excess and they were not allowed to change the condition of this under their franchise agreement with the DFT, but that situation also applies to condition 28.2 where they weren't allowed to change that condition under their franchise agreement with the DFT, i also made the argument under the legal statue above, they made a counter argument, but it wasn't a legally defensive position as the criteria for their defense was not applicable, once i informed them of that, they deadlocked the situation and maintained their position of not doing anything wrong.
Final Position:
1. I have a legal claim against them, but lets be realistic, its a £15 excess, it just isn't worth going to the courts for it.
2. I have sent an enquiring email to both the DFT and TheRailDeliveryGroup for clarification on who had the correct interpretation of the NRCoT conditions and for a further explanation as to whose position is stronger in this type of situation.
3. I accepted WMT offer so in total £47.55, the position of chiltern refunding the super off peak return is up in the air ATM, they've made no attempt to reclaim the £33.10 so technically speaking the total refund is closer to £80.60, don't know how that happened, but I've already checked legally, im not liable for Chilterns mistake and the act is on them to recover if they chose to.
4. I was contacted by the Office of Rail and Road strangely enough directly, as apparently their intrigued by the situation itself and the way it was handled and the positions each company took, why none of the companies interacted with each other regarding this matter, and the positioning of the The NRCoT conditions that led to the deadlock, i don't know for what end, but it is what it is.
I'd like to thank everyone that offered assistance and opposing views regardless if i agreed with yourselves or not on certain points, thank you for taking the time to share your opinion/expertise in this matter.