SP are possibly the post incompetent company I have ever dealt with. Over the past 4 years, they have:
1) Failed to bill the previous tenants in a shared house, and tried to get £1700 out of us. This was despite someone regularly coming round to read the meter. This went on so long we got Energywatch involved, and took about 18 months to solve, by which time we were moving out ourselves.
2) In addition, we were on pre-pay electricity, and managed to rack up £800 in one year as credit. They eventually refunded this after more threats from energywatch.
2) Once they sorted that out, they then managed to fail to change the names on the bill for the next 18 months...
3) At a different property, provided an extortionate estimated bill, 5 days after the meter was read
4) Rang me up on three separate occasions to get me to pay a bill that wasn't due
5) Sent me a red bill before a normal one for my final payment
6) Now refuse to acknowledge that they supply my last property, when my ex-landlady (she moved back into the last property I rented) moved back in. She's still had no success 1 month later!
Absolute idiots of the highest order. The worst part was the dual fuel bit, where they wouldn't use the excess in the payg elec to pay the gas, and refused to ever put you through to someone high enough up who could look at both elec and gas a/cs.