I would not recommend removing the feedback first, like S said.
Kia ora Howard, This website doesn't seem to be related to Trade Me; I highly doubt this issue stems from Ping. I would recommend contacting your bank via the number on the back of the credit card and letting them know about the continued unexplained charges - they would be your best people to contact.
You can refer to instructions on how to transfer money from your bank to ping account here Ping account – Help - Trade Me https://help.trademe.co.nz/hc/en-us/articles/360007264411-Ping-account
Yeah with that condition flossy63 mentioned, it's now clear to me Ping is more targeted at 'In Trade' high volume commercial sellers.
Just to add to that, I generally for most products there's a lot of price competition if it's the Chinese made kind-of-stuff stuff, so it shouldn't be hard to find someone else that accepts Ping. Otherwise, generally other sellers will inflate the listed price to incorporate the cost of Ping. If you really want Ping, and am happy to pay a little extra than the listing cost for this, I'm sure offering the seller an extra $5-$10 on listing price to cover the Ping fee might work with a little convincing.
I would recommend contacting Trade Me with this one - it sounds like a new technical glitch they may not be aware of. Submit a request – Help - Trade Me
Because accepting ping is expensive! Ping takes another 2% off the sellers bottom line - although on a small scale this might not seem like much, if a seller does $10000 in a year (though many do WAY more,) that's $200 which could be in their pocket which is instead going overseas. On top of this, for in trade sellers, some categories already have success fees of almost 12%. Yes, Ping might cost you an extra two-three minutes, but especially for trades $1000+ Ping costs the seller a serious chunk of cash. I don't know of a single trader selling cheap stuff (stuff like phone chargers, cases...
Recently, (more than usual,) I've found that my listings rank significantly lower than other similar listings in search rankings. Even if I temporarily use the *exact* same category, description, price and everything as a random listing above me, nothing changes (I change it back, don't worry.) I rank far higher feedback wise than those other random listings, so that can't be a reason, and my shipping prices are cheaper. I swear it didn't use to be this hard to achieve half-decent search ranking. Does trade me shadow ban people - that's the only explanation I could think of.
Something else I would like in regards to feedback is the opportunity to filter out all positive feedback, so you can view the negative feedback on traders more easily - this would make it far more meaningful. The feedback dispute process also sucks - I've had feedbacks placed (somehow) after the cut-off; worst one yet though is a feedback placed complaining the product arrived broken, despite the buyer admitting he broke the product by rough handling when unboxing it - that feedback still is up.