Trip.com complaint: Overcharged

On 3108 I attempted to purchase two tickets for 67 EU, I presumed the payment had gone through but 45 mins later I received an email to say it had been cancelled. I bought the same tickets immediately but was charged 33eu more. I proceeded to livechat to make a complaint and was told the tickets were 67eu, the original price and they told me to make a complaint in writing to trip.com. Trip.com will not take responsibility saying prices fluctuate constantly, this is untrue because I watched the tickets for weeks not sure if my departure date..the tickets remained the same price if 67euro. After I was charged 100eu I checked the prices and they were again 67. Trip.com scammed me out of this money as they said the booking was cancelled and to rebook was 100 so I had no choice but to take it. After I booked the prices went back down again. Please can you investigate this? Thank you