It appears there may be a system error as a few people have this 1969 issue. Another person just recently posted same issue with a screen shot.
I have an idea for you to try. However it is completely up to you if you want to try it or not. NO idea if it will work but worth a shot. If not you would have to contact the moderators and they will investigate for you.
So first.
Can you check your account again. Is there a balance in your account?
If yes, is the amount the same amount that you deposited for your plan?
Example $25 plan, $25 in balance?
You need to check credit card if that is all you been charged. If plan was $40 and that $40 is sitting in your account make sure you were only charged $40 on your credit card.
If you confirmed all that...what I am thinking is because of the 1969 date it did not debit the money from you public mobile account to activate your plan... as normally you PM account balance would be zero.
So you could try this.
Log into account.
Click change plan.
Select the plan you want.
Click "Change NOW" DO NOT click change at next renewal date.
Hopefully the system will process your plan debit you PM account balance..it will activate and instead of a Date of 1969 it will go to a current date.
Again completly up to you if you want to try it out...if you do, can you please post the outcome?
If you choose not to or it does not work you will have to contact the moderators. To do so on the bottom right have corner there is a question mark. Click that to talk to SIMon the chat bot and you will be able to open a ticket with the moderators to investigate.
