198339100

They keep calling and when I answer no-one says anything.

Had this number leave 16 messages last night some said "this option is not available" others were silent.

It has started happening again, calls every 30 minutes during the night.

I've received 30 calls on my work phone in the past 48 hours, all calls received late PM very early AM.
Please advise if you're getting these calls on your work/VOIP phones.
based on couple of my search results I am suspecting a Cisco phone system is initiating the calls. and no Voice message left.
Also one of the effected advised when he/she answered got a message saying this option is not available.
Hope that helps.

It called me last night the prefix was +03 198-339100 so it's originating from Greece.

Sorry typo it's +30 which is Greece.

I believe that it's Telstra trying to deliver one of those 10 second text-to-talk messages. Their system must be having issues at the moment.

While I have NO idea why I suddenly started getting calls from this service, it IS a text to voice service for SMS messages which cannot be delivered to your normal SMS number though when it calls my mobile there is no way to respond to it, only when it somehow got hold of my WORK number was I able to configure it. It appears to be a Telstra service ...
You can set the hours and the length of ring-time etc but don't yet know how to define what numbers it calls you on ...

Credit to "Alan_B" for an Excellent answer on http://www.findwhocallsme.com/198339100
Alan_B
5month(s) ago / 2014-05-06
In Australia 0198339100 is Telstra's Talking Text service

If you receive a call from this number it is someone trying to send you an SMS, it could be a friend that has selected your home phone number instead of your mobile by mistake.
If you have SMS capable equipment, T-hub or SMS capable handset, it will be able to receive the message, otherwise it will read the SMS out to you using a computerised voice.

When you pick up the phone, say something to trigger the delivery otherwise it will start in about 5 seconds.
It will tell you how many SMS messages there are in the opening greeting then begin playing the first message.
After it has read out each message it will read out the senders phone number and the time/date it was sent. If there is more than one message it will read out each of the messages in the order they were received. Each message is deleted once it is read.

During the message being read out you can press:
1 to replay the message
2 to reply to the message
5 to delete the message ( if there are more messages, it will begin reading the next message )
6 to go to next message ( it will automatically delete the previous message )

Reply messages:
1 yes
2 No
3 OK
3 Please call me
4 I'll call you later
5 Smiley face
6 Sad face

Once all messages have been delivered you will be given the option to go into settings by dialling 3
In the setup menu you will be given the following options:
(1) Delivery mode – Talking text only or Auto detect(doesn’t apply here)
(2) Night Time – ( see below)
(3) Ring time – (See below)
(4) CLIR – for silent line services that wish to send messages

Night time:
You will be given these further options
(1) Set non delivery time to Midnight to 8:00am ( this is the default setting)
(2) Set delivery to 24 hours
(3) Customise delivery time by setting the start and end times to times that suit you

Ring Time:
Set it to a custom value to hang up before being answered by an answering machine.

The service will also do its best to translate SMS acronyms like LOL, ROFL AAMOF :) :-( etc
Don't send emoji or emoticons.
If you are sending from a mobile to a fixed number, make sure you include the area code in the number you are sending to.

If you are with Telstra, you can dial 0198339999 to access pending messages or change the settings ( don't call 0198339100).

If the phone only rings once, it usually because of an SMS capable handset trying to receive the call. If the memory is full, the handset will not be able to receive the message. If there are two SMS capable handsets on the line then they both will answer the call and cause confusion, in this case, consult the instructions and set the "Terminal ID" to 0 on the main handset and 1 on the second handset. This will make the handsets answer separately. The terminal ID is sometimes called "Box Number" and is usually found in the SMS settings.

On request, Telstra can also block receive SMS messages from being delivered using this service. If doing so, and if you have a self monitored or back to base SMS capable burglar alarm, make sure that you only block receive SMS ( not send SMS as well) otherwise you may not get your SMS message being sent from your alarm when you need them.

Although I am Telstra staff, any views express are my own and don't necessarily reflect those of Telstra.

Answered call and voice stated there was a voice SMS for us.  An automated voice then said "Sorry I can't talk now".

message stated new number for mini mini ha ha or some crap similar...why TF bother at all

Suspect call probably scam