Only the administrating unit can make changes to PAX, but if call the number the Customer Service Centre will send you the correct form to give to your HR staff.
PAX should not be started, stopped or changed without the correct JPA form as it requires your written authorisation (and the RAOs) to be valid. This is all to reduce the risk of fraud and to ensure that your cover is only cancelled when you want it to be cancelled.
Slight confusion on my part. If, while you were deployed, then you were involved in the AD side of things then I would assume that you would have a pretty strong case for pushing your CoC on this one. If you were beavering around some PB or FOB - but using an AD PID - then you might find that people are less in a rush to fight your corner for you to receive specialist pay for a specialist job you did not do. Anyway, if the former good luck and keep chasing your CoC.
You are correct, RPAX is normally the most appropriate product in the PAX range for someone in the TA. However, on mobilisation troops are offered both products and some elect to take PAX because there is no danger of a DD payment failing and their cover lapsing whilst they are away.
In the case of PAX, cover will only stop if the policyholder cancels the plan or if they are discharged. If there as been an error as you were processed through RTMC then you can apply for a refund on 0800 212480.
On the broader issue, I appreciate that you know your clerk, but difficulties have arisen in the past.
For example, if someone had not signed the form to say that they wanted to cancel the plan, the clerk cancels it direct on JPA and the soldier then suffers a covered injury, then they have grounds to say that they are still on cover and the clerk is in the proverbial.
Or, someone goes into their admin office and asks to increase to 15 units and the clerk does the change on JPA without the form. That soldier then suffers a covered injury and discovers that the clerk typed-in 10 units by mistake. The only record with the correct authorisation is actually what cover was in place before the change, but the pay statement indicates that ten units were held and this would be honoured. However, there is no record for the 15 units the soldier actually wanted.
Without the paper-trail it is very hard for either side to prove what cover should have been in place. It may seem like a pain, but this system allows troops to take out or change their cover whilst deployed, and for that cover to start the minute the RAO countersigns the form.
We can get the relevant forms to units fairly quickly - although the BFPO system can sometimes slow things down - and there is no real excuse for a unit not the have a stock of the relevant forms to hand.
In this case, it would have made no difference if you'd cancelled the plan on the date of your original post or if it happens in a week's time. It will run as is until the end of this month and then payment will change on the 1st of the following month - as long as the form is handed-in and the JPA action completed before the last pay run of the month.