"After having previously been caught out on a rolling contract which Southern Electric alleged they had sent a letter about, I was determined not to let the same thing happen and carefully noted when each contract was due and gave the required notice.
"However, when I rang British Gas to take up a quote I had from them, I was told that by law it takes them 28 days to take over the supply and that this applied to all. So we carried on, and I have now received a final bill from Southern Electric, for which they have increased the unit charge from 8.54p per unit to 30p per unit.
The upshot of this is that the bill comes in at £3,283.55 instead of £1,763.85, and they are charging me more for the final 21 days than they did for the previous two-and-a-half months.
"When I wrote to them they told me that, as my contract had ended, I would automatically go onto their standard tariff. As they have to purchase energy in advance they cannot pass on the benefits of reduced/fixed tariffs to non-contract customers."
Teresa says she feels as though she has been "done up like a kipper".
I had to tell her that she was the third retailer in a row I had heard from with these sort of problems that same week.
Apparently, Ofgem is aware of the sneaky 'assumptive renewal' practices that stick you on a standard tariff when you haven't managed to switch, so I would advise anyone to complain to them (020 7901 7000) even though I don't think they will give any practical help.
I consulted Energy Helpline (part of the Make it Cheaper Group, tel: 0800 970 2626) and spokesman Nick Heath tells me that he is hearing prices up to 32p per unit at the moment.
Helpfully, he sent me a case study of Bigbury Post Office & Stores on the South Devon coast. With chillers, heating and lighting on the go all the time, the shop's electricity meter is dizzy enough to clock up about 27,000 units a year. At 8p/unit and an annual standing charge of £230, this has been costing proprietor Carolyn Hunt about £2,400 for the past three years.
However, as her contract was due for renewal she received a letter from her supplier at the start of the year informing her the rates were about to double (to take into account the price rises that have taken place since the start of her contract in 2006).
This prompted her to reply with a termination letter and shop around for a more competitive rate. Selecting several price comparison services via the internet she was pleasantly surprised at how easy it was to obtain cheaper quotes over the phone.
Make It Cheaper came up with the best deal - at 10p/unit and £50 a year standing charge as a 'new customer' with Scottish Power. Although this is slightly more than she is used to paying, it is significantly lower than the renewal price her current supplier was suggesting.
She instructed Make It Cheaper to switch suppliers on her behalf - which it did without charge. As a result, Bigbury Post Office & Stores is safe in the knowledge that it is unlikely to be paying any more than £2,900 a year for its electricity for the next three years.