Can't get my PAC

Here’s something a bit odd………

I currently have a Tesco PAYG account , the number from which I wish to keep as it’s so well-used and everyone knows it. I texted ‘PAC’ to 65075 as per the id website instructions .The text seemed to send correctly , but I instantly received a reply from O2 , saying a PAC could not be issued , as there was a ‘problem’ , and to try later or go online to O2. I am not aware that Tesco uses O2, but that does not mean they don’’t . …...I’ve just checked , and it IS O2. I have a grand total of 4p credit left, and this decided me now was a good time to switch . Could the issue be that 4p is not sufficient credit to receive the PAC text? I note that  the 4p credit did not change upon sending said text . I am reluctant to put any credit onto the Tesco account, as I’m sure there’s a minimum amount, and that’s a bit stinky as it won’t get used , unless Tesco send me a different number to continue with , then I can burn up that credit ? Or, is it likely to be due to the fact that my id sim has not yet been used? I’m waiting for a new ‘phone to arriive so have had no need to use the sim yet, and anyway , I’m expecting an important call on the number I wish to keep, so Im delaying the big switchover until such time as I can be incommunicado for a while. Just thought it may be prudent to get the PAC in advance . Any ideas , folks?

Wait a minute !! Sorted it, seems the PAC request is case-sesitive . D’OH !