Can my bank cancel a standing order I have set up without my permission or notifying me ?

I have two bank accounts, one with Santander and one with NatWest. I haven't used my Natwest account in a year, however I am currently paying off a small loan and had used my �600 overdraft to travel and as emergency money. I occasionally went a few pence over my over draft but predominantly stayed at �570 something, therefore not actually exceeding my over draft. Having found somewhere to settle, I opened a Santander account for my wages to be put into since there is no Natwest where I am. I asked Santander in February to set up a standing order, whereby �15 every Thursday was to be transfered into my NatWest account. I checked my accounts the following week and saw that the standing order was in place, and felt secure that I needn't worry about any charges for being over drawn on my over draft etc. I recently got a call from Natwest telling me that the loan I have been paying off has been returned unpaid, due to lack of funds in my account. I disputed this, saying I had in fact set up a standing order. NatWest proceeded to tell me that only one payment was ever made and I had thus incurred upwards of �190 in charges. I spoke to a lady in Santander and she ured me that the standing order was still running... But then decided to tell me it had been cancelled. Then she told me it was still in place. I asked her to ensure that, unless under instruction from me, the standing order was to remain in place until I further notified them. I am still, 3 weeks after this farce, in disputes with NatWest, who are charging me stupid amounts in interest and charges, yet they know I cannot afford these charges. After all, they have access to my bank accounts and have attempted to set up a repayment plan for me, to no avail since, for every �15 a week payment that was agreed between me and NatWest, they are seemingly charging me interest still, as well as a random �28 charge a couple of times a month. Since I don't have the funds to pay these charges, they then charge me again for not being able to pay the first lot of interest and charges. Is there a loop hole by which I can get out of this? They have told me the only way I can deal with this is by putting extentions on my over draft, which means I'm still getting charges and interest charges to an account of which I have absolutely no funds in and yet they keep taking money. Also, would I be within my rights to take a copy of the first lot of charges accrued to Santander and demand they pay these, as I was completely unaware that they had stopped the standing order that was to be paid into my NatWest account? I'm 90% sure the banks cannot keep getting away with charging people ridiculous amounts like this. As I said, it's seemingly a case of I put �15 in and they want �28 which I don't know about until the end of the month. And that is on top of sporadic interest charges of �10 plus. Can someone please tell me why they are doing this and how I can dispute this. Because of these silly charges, and because I'm transferring a minimum of �40 in just before the 10th of every month to supplement my loan repayments on top of the �15a week, I am struggling now to even pay my rent. Advice, please!!!!! =(