Here are the exact chargeback rules of PayPal. What I do not know is, even we can prove that a certain transactions of Bitcoins are succesfully done, PayPal might not reverse the charegeback.
https://www.paypal.com/uk/webapps/mpp/chargebacksWhy do chargebacks occur?There are a few reasons why a buyer would request a chargeback:An unauthorised payment was made with the buyer's card
The buyer didn't receive the item that was paid for
There were errors in processing the transaction
The item does not match its description
The maximum time a buyer has to file a chargeback with their credit card company is typically 120 days after the expected delivery of the agreed goods or services. Certain exceptions may apply.
How do you dispute a chargeback?If you wish to dispute a chargeback, you will need to provide certain information and evidence depending on the case. Below are the two most common reasons for chargebacks and the information you need to provide in each case:
1. The buyer didnt receive the item
You must provide either:A tracking number as provided by Royal Mail Recorded Delivery and Parcel Force 24
Proof of a refund this can be evidence from your PayPal account, the back and front copy of a cheque, or a money order used to reimburse the buyer
2. Unauthorised use of credit card
You should provide:Tracking number for delivery of the item
Proof of a refund this can be evidence from your PayPal account, the back and front copy of a cheque, or a money order used to reimburse the buyer
Any communication from the buyer, such as emails or positive feedback on eBay
Any contracts signed or information on the sent item
Date that the item was sent and the address it was sent to
For intangible items or subscriptions any information regarding the item or service
In these and all other chargeback cases, the more relevant information you can provide, the better your chance of reversing the chargeback.
Tips to help avoid chargebacksTrack your delivery: Always use a postal method that provides online tracking and proof of delivery, which you can send to the buyer as soon as you have a tracking number
Be accurate: Describe items in as much detail as possible, so buyers know exactly what to expect and cannot claim that an item is 'significantly not as described'
Know your customer: Ask for more information such as their full name and address, get in touch with them and review eBay feedback (if available)
Deliver on time: Always post your items in a timely manner - where possible, you should aim to dispatch your items within seven days of receiving payment
Be transparent: Make sure that buyers know about your returns policy
Be responsive: Don't let buyers feel that their problems are unresolved
Post carefully: Avoid posting to an address different to the one provided by PayPal
High-risk countries: We advise extra caution when posting to Macedonia, Lebanon, Ukraine, Lithuania, Nigeria, Romania, Pakistan, Bulgaria and Indonesia.
Check ID: If a buyer collects an item in person, ask them to bring along proof of identity. If another person is collecting the item, they should also bring proof of identity and a signed note from the buyer authorising them to collect on their behalf. Note: Payments received in person are not covered under the Seller Protection policy.