The rental company forced me to purchase full car insurance without my knowledge and did not confirm that this was a reimbursable expense, which violated my personal interests.

Although we had purchased full insurance, the staff added super full insurance without our consent or any explanation during car pickup and just asked for a signature. We didn't check the bill carefully and signed, resulting in an extra 3000 RMB cost, which made us very angry. The same thing happened to the three foreigners before us. Be cautious, thoroughly check all charges and ask for explanations before signing anything to avoid being scammed.

The car rental company didn't clearly explain that their insurance and the insurance I bought on the rental platform are separate and would cost extra.

Do not use this company. At pickup, they claimed I didn't have insurance (even though I had bought insurance through the rental platform) and forced me to buy additional insurance for around 10 euros per day. I strongly refused, she still insisted and then claimed my credit card limit was insufficient (they wanted to reserve 3000 euros, and my card had over 4000 euros available at that time). I had to buy the insurance to reduce the required credit limit. Finally, I thought I'll only visit Belgrade once, so I bought the insurance... In the end, they charged me over 1500 RMB for some unspecified additional fees during the 6-day rental. Avoid this company at all costs!!

Avis Belgrade, is pretty slow in service. Though pickup didn't bothered me much, drop off took almost 2hrs. Luckily I had time in my hand or else I would have missed my flight. There was a minor scratch on the car for which they charged me almost 400 euros. Bad part is the charge was mentioned on the invoice as insurance premium. Thanks ERC, they managed to convince Insurer about the genuineness of the charges.

Price drop protector is a great option. It saved me 10% as ERC auto booked me with lower price. ERC was also very co-operative in helping me on insurance claim. I have purchased additional coverage from them which took care of access charged by Avis.