"It says 18/03/19 for the transfer date. Lol I jus really need my number to be transferred as soon as possible. "
So your number will be transferred Monday. There is absolutely nothing you can do at this point that will speed this process up.
(note that all UK networks use the same process & contractor for transferring numbers & that no work on number transfers is done at weekends or on public holidays for any UK network.)
As you submitted the transfer request after 5pm, the earliest that your nunber can transfer over is Monday the 18th
You can still use your previous network sim right up to the time it loses service on the 18th
Could I ask is your previous network sim a contract or payandgo?