I'm not sure if this should maybe be a topic in itself as I was not notified of this change by SS,
but posting this in case it might be helpful to someone and in hopes not more of us make the same mistake so we don't suffocate the CS.
I went to Sideshow website today as I usually have some POs on a 'Payment plan' and I often make my payment earlier using 'Make next payment now' option.
Today I've noticed that there is 'Pay towards balance' option instead, so I used it only to find out the entered amount (instalment amount) was just deducted from the total amount
and remaining monthly payments were reduced, but I was still due for the current month. (they fixed it)
I contacted SS regarding this and the 'Make next payment now' option can now be found under 'Modify payment plan'.
The last time I looked at that option it was only for a 'change payment date' but now there are more options within it.