Looking for a Cheap mobile provider

Hello,

Looking for a cheap mobile provider for two GSMs for the family.

Already have one subscription with proximus post-paid "smile 5" for  5 euro per month. Can't use free 30 minuts anymore as this free minutes are with  another proximus user only. So end up paying 5 euros a month for nothing- just to keep such a chepa postpaid subscription.

Would like to Keep the current GSM number from  proximus . Not sure if I need to switch to other network or take another subscription from Proximu

Use VOIP from PC to call internationally, have FTA satelite TV,  ADSL from Skynet, use GSM to call the family. So, no need of plan to tie, data, voice, vidoe together.

Used lycamobile before but looks like it is not an option anymore. Lycamobile to Lycamobile calls only free after you buy x amount of credit and is vlaid a month or so.

Requirements as follows:

Want:

• pre-paid or post-paid, cheapest possible
  
• calling family for free  or cheap, conversations for a minute or two each time
  
• calling another friend who is on base( or asking him/her to convert to cheap network we choose)
  
•   usage forseen less 30 minutes per month, 15 minutes to base, 15 minutes to same network in the family
• only phone, no dataplan
  

1. What is best in our situation? pre-paid or post-paid?
2. Any suggestions or Any promotions you are aware of?

Thanks in advance