There are two types of leverage they might be asking about with these types of questions:
> The theoretical maximum leverage available due to the margin requirement settings of the contract - which is fixed at 20% of the notional value of the trade (this is a fixed percentage), and
> The actual leverage they use in their account - which is determined by the trade size they open relative to their account equity (they can choose this when placing a trade)
The client can trade without leverage by simply opening a smaller trade size, provided they have account equity of at least the value of the smallest trade size of 0.01 lots.
As an example:
If a client opens a 0.01 lot BTCUSD trade and the current price is 43,000 USD - then their exposure on this trade is 0.01 * 43,000 = $430 USD
If they have 1000 USD in their account, then their actual leverage on the position is less than 1:1 - as they have $430 USD of BTCUSD exposure with $1000 USD of account equity
This assumes they don't open any other trades, which would increase their total exposure.
So, it's worth pointing out when we receive these queries that while the margin requirements of the contract are fixed, they can trade with lower leverage by opening a smaller trade size - they do not need to open the maximum possible position that the leverage allows.