No, this is not Royal Mail. If you get a call appearing as 07746 726213 or +44 (0) 726213 then you have been contacted by scammers.
They are, to put it simply, trying to get your bank details. They have tactics and these are to try to convince you that they are Royal Mail and they have a parcel they want to re-deliver. They will continue, with willing participants, to try and extract personal details and bank details. Thee they will use for the purposes of fraud. Put teh phone down, report, block. No good can come of any interection with the phone number 07746 726213. Royal Mail post cards through your letterbox if they need to re-deliver. They do not phoen you through a UK mobile. Be suspicious of any contact pertaining to be from Royal Mail, especially by phone. Better to be safe that sorry.