Sorry, but this is one of the major pitfalls of buying SD cards from unreliable sellers. Counterfeiters take a smaller capacity card and program it to make it read as a larger card. So in your case, it's possible it was a 32 GB card that was programmed to read as a 64 GB or 128 GB card. Or maybe it was even smaller, like 4 GB, and the size that's displaying is completely inaccurate due to the tampering. In any case, these cards work fine as long as you haven't exceed their true capacity--but once you do, some or all of the data on the card might become corrupt. No one else has your data, so you don't have to worry about security breaches--but the data itself is probably unrecoverable.
Avoid buying SD cards from random eBay sellers. Stick with well-established retailers--preferably bricks and mortar stores like Best Buy or CostCo, or online retailers with good reputations and good return policies, like Amazon.
Even with genuine cards, always remember that SD cards are not forever--they can fail unexpectedly, due to defects or to wear and tear. So always keep important data backed up on your computer or in the cloud.