When setting up your account you may also choose to impose a ceiling on the maximum deposit you may make within a specified period of time.
Daily: within a 24hr time period
Weekly: within a 7 day rolling period
Monthly: within a 30 day period.
Any decreases to a deposit limit are instant, any increases have a 24hr wait before becoming active.
Mandatory deposit limits are imposed by the compliance team for a number of reasons, to increase any limits they set, you will need to get in touch with support who can assist.