I missed a few episodes, can someone please explain why Maria is texting Tyrone pretending to be Kirsty? Does she want to get together with Tyrone? What happened to Marcus after his affair with Todd got discovered - is he still with him?
You seem to have missed quite a few episodes. Marcus went to London for a while. Maria is trying to get back to Tyrone. By texting pretending to be Kirsty she has created tension between him and Fiz, they have been quarrelling a lot as he's confiding in Maria and not telling Fiz about some of the text. Maria is being a bit devious. She is lonely and wants a fellow.
But even on payg phones in UK and Europe when you buy a new SIM and/or phone you have to register your name, so the Police could soon trace it to Maria.
You don't have to register your name with a payngo phone Netti, that's why Maria hasn't been found out yet. David knows it's her but Fiz can only get the phone number and doesn't know it is her.