PAYG Sim cards

[brickwargames]

Been selling PAYG sim cards with good numbers for years on ebay. Just recently the listings are getting removed after a few days saying they are violating a policy, even though they are not. Ebay says someone reported the listing. Obviously a rival seller. There are hundreds of similar listings.  How do I prevent this happening. Its impossible to speak to a real person  with any authority on ebay help. 

[plpmr]

Perhaps the question is being asked - how can a private seller be holding stocks of and selling genuine brand new items.

[brickwargames]

Thank you for your informative and knowledgeable response. No doubt ebay community is a much safer place with you patrolling the forum and bestowing your wisdom