pleaseBy call out I assume you mean urgent, unplanned, unsociable hours type work. It is generally accepted that this type of work costs more than pre-booked normal hours work. All you have to do is decide what percentage multiplier you want to implement to ensure you are making a good return for the extra hassle of the work which may cause disruption to your personal commitments or other planned jobs. If you breakdown on the motorway and have to call a mechanic out it costs an awful lot more than if you had booked you car in to a local garage for some work. Most reasonable customers understand this concept of increased charges, however if they don't, then you are probably best not doing the work in the first place. I would imagine you have to start at time & half or double times your normal hourly rate to even consider going to the job.
And your customer will also know the quality, standard and reliability of your work and they will know you will do a proper job, not cut corners, not rip them off, But charge a reasonable rate proportional to what work is done. Anybody with their head on the right way up will be willing to pay a premium for quality work done outside of normal working hours. If you under price yourself for out of hours call out work it can make it harder to justify your normal hours rates.
