No response on request for Surname and Title change

I sent a copy of my marriage certificate and ID on the 19/03/2019 to your documents department to amend, as my statement still had my ****en name and it also stated MR not Miss or Mrs.

I am very disappointed, as I received my new statement and invoice yesterday and still it show the old details.

Please tell me how long does it take to do a simple change of surname and title on your side, as it has already been 3 weeks????