Impossible to get a refund. Awful experience!!!

In October 2014 I booked a return flight to Russia (to the Crimea via Moscow) using Opodo service. The departure date was 16 December 2014 from London Gatwick early in the morning. All was fine (despite the fact that Opodo kept reqesting my passport details every now and then and I kept replying with my details, coupleof days after my emails I used to raise enquiries on Opodo webside asking if they were in reseipt of my details but did not hear back from them).
In the evening of 14 December I decided to check the flight status on checkmytrip.com and it appeared that my flight date to the final destination was changed without any notifications, another date was absolutely unacceptable. I raised an enquiry the same moment on Opodo website - no responce, phoned them on 15 December first thing in the morning (my coach to London Gatwick was departing the same day late in the evening), after having spent easily an hour I was assured that either Opodo or the Airline itself will contact me by the afternoon to give me an update. I even found a flight with the same airline but from the different airport in Moscow and simply offered Opodo to re-route my trip. Anyway, I had to phone Opodo myself in the afternoon as I did not hear back either from them or from the airline, spent around 30-40min simply waiting for the operator to answer the phone, noone answered. I had to book a flight from Moscow to Crimea myself which was only £50 but was the last ticket available under such price.
When I was almost on the way to the coach station after 6pm Opodo contacted me with a good news (as they said) - they had cancelled my whole trip!!! I went furious, people I was talking to in the morning and in the evening spoke terrible English and obviously couldn't get what I was saying, that is why they messed up with the whole trip. I had to ask to put me through to the manager, not sure if it was the manager but he appeared to be quite helpful and polite.  He had to rebook my trip, I had to agree to the dates but told him that I will request a refund from Opodo of the trip from Moscow to the Crimea and told him that I have booked the flight to match my trip arrangements.
To cut the storry short, the flight from the Crimea to Moscow was also rescheduled and I had to buy additional ticket and had to take taxi in Moscow to get from one airport to another.
Once I was back to the UK, I had contacted Opodo, describing all the story in details with exact amount of extra expenditures which I was asking to refund. In a month I had to contact them again as I did not hear from them with any kind of confirmation, total disregard! I received an email from the Customer Service operator saying that they will not refund anything and that their record shows that Opodo did contact me with the flight changes on the 08, 12, 13 and 14 December asking to confirm the flight alterations but they did not hear back from me and that it is not their responsibility but the airline's who I was flying with...  In fact it is their responsibiloty as they are the intermediary company reponsible for all the arrangements, that is exactly what they are getting their fees for.
After the Customer Service Operator's email I contacted Opodo asking to review my complaint and another, competent person to deal with my matter. I still have not heard from Opodo.
I will not leave this case until I get a reasonable answer from Opodo. I read through FAQs regarding flight cancellation policy and re-routing, it clearly prooves that my flight must be refunded or at least they were supposed to re-route my trip the same way I did.
I am a frequent traveller and have used so many airlines services and travel service providers, have never had any issues, including getting refunds when my flights were re-scheduled/cancelled, but Opodo service is outrageous. Never again myself, my family and all the friends will use their service.