The punting sim is the best idea, and one that would ensure no transfer or potential "wrong number" calls.
In relation to the numbers and texts, as I also have to ensure no trace left, all calls are deleted as are texts immediately. Like mission impossible, but they don't self destruct... The only other record is the phone bill which arrives to the place of work and is not a personal phone.
I am however going to invest the tenner in a SIM now and convert to the using this to book appointments in the future.
On reflection, I'd think the best policy for the ladies is to not call back at all, typically if I've missed someone, I try again in an hour or so.