So Energy - failed to transfer me onto the agreed fixed nearly 6 months ago

Sniblet

I called So Energy in March to fix my tarrif to the new So Guava fixed for 2 years; I did the calculations and the offer was in the range Martin had suggested (at the time no more than up to 20% over the current March 22 price cap). 
Imagine my surprise when they failed to switch me putting me instead on their standard tariff (presumably so they can charge me the earth come Sept).
I've emailed several times complaining and have received responses saying they're looking into it but no official response yet and we're coming up to the 6 month mark!!!!
What's my next course of redress?
Any advice gratefully received. Thanks so much. S

pochase

Did you get an email confirming the new tariff?

When did you start to contact them about it? Can you give a short timeline?

Did you raise an official complaint and when?

Sniblet

Awww thanks for the message.

They never confirmed it but their calls are recorded so they heard the conversation as I made a note of the date/time and whom I spoke with. After at least 5 emails and 2 phone calls I threatened the Ombudsman via email and said 5 months is not acceptable in anyone's books (despite them being so busy) to put me on the right tariff.

I got a phone call on Bank Holiday Monday just gone and they made me an offer I couldn't refuse so it was sorted. Thank you @pochase for taking the time to message me.