To lower the price for a certain listing, call the lowerOrderPrice method:

// Get valid orders for an NFT id (Multiple orders may exist for an ERC-1155 NFT)
const orders = await getSellOrders(
  network,
  maker, // Maker of the listing
  tokenAddress, // string, contract address of NFT collection
  tokenId, // string, token ID of the NFT
)
await lowerOrderPrice({
  network,
  signer: seller, // Signer of the seller
  order: orders[0], // Pass in the order you choose to lower price from above.
  price, // string, sale price in wei eg. '1000000000000000000' for 1 ETH. Must be lower than the current price.
  expirationTime, // number, the unix timestamp when the listing will expire, in seconds. Optional. Must be at least 15 minutes later in the future. If the current order is going to expire within 15 minutes, then a new expirationTime must be provided.
})

By using this method, the current order will be cancelled off-chain and a new order with a distinct 'orderId' will be created. To get the new 'orderId', call the /v1/orders?token_id=&contract= endpoint.