Question : Problem: Modem bank authorizations fail to connect - just constantly redials bank

I'm the IT Manager of a small mail/web order business in the UK and we're having problems authorizing card payments. Basically every time someone pays via a card the number is authorized before the money's actually removed from the account - It's how we can send things out next day without actually taking the funds. Our system does this by using software from commidea which, over a modem, calls the bank and batch authorises the transactions. Once authorised the transactions can go to picking, then posting etc etc.

All was fine until 18th September when for some reason when the modem called the bank it would not have any response and just attempt endless redials. Calls are definitely answered, but are not progressed to authorization. The modem's log file is as follows...

08:03:22.15 SendBlock (ATDT08003850133, 16) /*call 08003850133 */
CONNECT 2400 /* attempt to connect at 2400 bps */
08:03:41.79 SendBlock (A34, 4) /* modem sends propietry data 'A34' likely the beginning of the bank's handshake protocol */
08:03:44.81 SendBlock (A34, 4) /* I assume no reply within 3 secs so it tries again */
08:03:47.82 SendBlock (A34, 4) /* again no reply to it tries for a final time */
08:03:50.84 SetDTR (Low) /* Setting pin 4 of the RS232 low to signify its ready for data */
NO CARRIER /* call terminated */

What should happen is something like this&

09:44:57.48 SendBlock (ATDT08003850133, 16)
CONNECT 2400
09:45:14.43 SendBlock (A34, 4)
/* bank responds */
09:45:14.71 SendBlock ([merchant id][cc number][auth numbers][auth numbers]S>32S>f, 74)
&

So nothing happens because it can't negotiate the handshake. The interesting thing is that the transfers do occasionally go through - but only once in every ~15 calls.

To remedy this I have...

Replaced the modem's driver, the modem's parallel cable, the modem's power supply and the RJ11 phone cable. Replaced the entire modem - still the same symptoms so clearly the modem can't be at fault.
Attempted calling my mobile from the modem - pass, it rings fine so our line is fine.
Attempted connecting to the UK2 free dial up service to test the modem's data lines, all connected fine, data exchanged fine etc so our line is definitely fine.
Tested connecting to that line at 2400 baud (the card authoring rate) to see if it was our line's noise at fault - fine, even had a BT engineer out twice to test the line and they've given it the all clear, twice. OUR LINE IS 100% FINE AND OUR MODEM IS FINE. I've tried another analogue phone line but the same problem exists.

I've tried using a completely different computer with a completely new build of the commidea software package - still the same problem. I've also tried calling from a location 20 miles away, but again the same problems. Commidea have been very helpful but they admit they've run out of ideas.

Last week we tried calling the bank's helpdesk and they admitted that they had had problems with those phone lines because of a switch of service provider. She mentioned something to do with changing to Virgin Media, probably because of the bank being bought on Tuesday by Lloyds. Since the 21st September however they've confirmed the lines are now clear of faults and claim nobody else is experiencing these issues.

So - since I've rigorously tested our own hardware, replaced the software with known working builds and BT have twice tested our line - can I only assume it's a problem with the bank?

I can't help but think it's an issue with the bank changing its telephone provider or another issue arising from their recent sale to Lloyds. Especially since the authorisations do go through once in every ~15 calls.

Answer : Problem: Modem bank authorizations fail to connect - just constantly redials bank

This issue is still a problem for us and its a shame that we're having to change to a completely different authorization package at a cost of £12,000. They had us by the short and curlies.