Ay sis, nakaka-relate ako sa situation mo! So from what I understand, kasi nag-file ka ng MAT1 with your maiden name in January, then nag-change ka ng surname sa April pero nag-claim pa rin with the old name, yan talaga ang issue. A few of us moms have learned the hard way na dapat talaga natapos na ang surname change sa SSS bago mo i-file ang MAT1, or kahit MAT2 pa lang. Kasi the system gets confused kung mag-mismatch ang names between your contributions record at yung claim.
Best move mo: personally go to SSS or contact them directly (not email, better if direct kasi mas mabilis ma-clarify) and explain na may name mismatch between MAT1 (old surname) at MAT2 (new surname). Baka kailangan mo mag-file ulit ng MAT2 using your current SSS records with the updated name, or they might ask for affidavit or marriage cert as proof. It's a hassle pero doable naman, at least you can get it sorted out before benefits expire!
Hopefully ma-resolve mo agad, friend. Good luck!