Also my pictures messages have been taking a very long time to finally go through, are yours coming back with a error message or just keeps saying sending? My last one took about a minute to go through which is very odd but it finally went through, so if it's not going back with an error message maybe wait a little longer but definitely check your self serve for a data block.
If you do have a data block but do not want to use other data besides to send/receive photo texts (mms) then you can purchase an addon for $2 that will allow the photos to go through but block all other data.
To take a screenshot with your S5, press the Power and Home buttons simultaneously. The screenshot will likely be stored in the Pictures folder or there may be a separate folder named Screenshots.
Try the APN configuration below. Some of the fields may not appear on your device. Test the new configuration using the built-in messaging app - Messages. Disable Wi-Fi if enabled. Mobile data must be enabled in order to send MMS messages. The data used to send MMS messages is not chargeable to you. Since you do not have a data booster, you won't have to worry about apps consuming data in the background. Let us know if this works.
Proxy: Not set
Port: Not set
Username: Not set
Password: Not set
Server: Not Set
Multimedia message proxy: mmscproxy.mobility.ca
Multimedia message port: 8799
Authentication type: None
APN type: internet + mms (or try default,supl,mms do not leave spaces between commas)
APN protocol: IPv4
APN roaming protocol: IPv4
Turn APN on/off: APN turned on
Mobile virtual network operator: GIDMobile virtual network operator: 4B