Me again.

So after waiting for 6 weeks I got a letter yesterday stating that I only get £27 a week and they will be in contact within two weeks to pay more NI and then review the whole thing again 6 weeks. I’m having baby tomorrow. This is so frustrating did anyone else have this? It says not too ring but wondering if I can and pay by phone quickly. Also I paid like £200 NI in May for 2018-19 so not understanding how I suddenly haven’t paid enough.... made sure I was up to date before claiming..