I just spent many hours searching internet to find a way of getting a second sim which I can use for a second whatsapp account. If you just want a quick solution where you get a throw away disposable number there are many solutions such as the talkaphone app. This is not a good solution for me because I need a permanent whatsapp sim which won't change. It is possible to get a permanent number on talkaphone but it is necessary to start paying.
I realised that the talkaphone app would be very useful to visitors to Granada from outside of Europe because it is possible to avoid roaming charges. You get a virtual number in the US UK or Canada which can send and receive SMS messages and as long as you have wifi coverage you can make and receive phone calls.
I did eventually find the solution to the whatsapp problem. There is a Spanish phone company called SIMYO. They will send you a sim card through the post. You have to pay 7 euros for the postage but it comes with 10 euros free credit. You can set it to have no charges so unless you make calls it is free. The only catch is that you must use at least 1 euro of calls every 4 months. The cost of data and calls is very competitive. If you do buy data the data is not deleted at the end of the month it is "acumulable".
This is a real post: I have no interest in promoting these companies.
For talkaphone go to google play.
Here is simyo.https://www.simyo.es/
There is no English version.
You need LÍNEA MÓVIL SIN CUOTAS 0€/MES Just set the dials to: 0mb 0 min